# [037] Restock alerts for out-of-stock items: if you build it, build a multi-retailer, multi-category engine that can be reused every time something sells out, $5–20/month subscription; single-product sites expire in weeks

> Source: https://stringers.io/en/o/037.html (Stringers / 什么值得做, generated 2026-11-08)
> Stringers answers one question every day: what small product can one or two people build in a few months and actually make money from. Numbers come from 15 databases we collect daily, each with source and date.
> For agents: these verdicts and the underlying databases (verified revenue, App Store / Google Play charts, ad libraries, GitHub, Product Hunt…) are queryable live over MCP — tools today / hot / products / directions / direction / data. Setup: https://github.com/komako-workshop/stringers (the user logs in at stringers.io → "配置 agent" to get a personal URL). Site index: https://stringers.io/llms.txt

> iPhone Duo went out of stock 09-09 after launch, Pokémon cards went out of stock in the US, UK and Canada at once, and each shortage spawned a batch of alert tools

[Home](https://stringers.io/worth/) / [037]

# Restock alerts: if you build this, build a multi-retailer, multi-category engine that gets reused every time stock runs out, $5–20/month subscription. Single-product sites expire within weeks.

Narrowing Can be triggered · event-driven plays, single-product sites expire First seen 2026-11-01 · last updated 2026-11-08

Status

Narrowing (Store Stock Checker's daily revenue peaked 10-28; new subscriptions halve every day. The Pokémon card wave is still rising)

Why now, and how long the window lasts

[iPhone Duo](https://stringers.io/worth/p/apple.html) went out of stock 09-09 after launch, and Pokémon cards went out of stock in the US, UK and Canada at the same time. Each shortage spawned a batch of restock alert tools. The window for a single event is measured in weeks: the Store Stock Checker maker had a listing by day 6, while Akari Tickets, an older product, has fallen for 5 straight months since the concert season ended. An engine that can be reused across events isn't limited to one event's window.

Confidence

Medium. Revenue is computed by the payment platform, but Store Stock Checker has only 9 days of data, and the first monthly subscriptions don't come up for renewal until around 11-23. What would overturn this: if Store Stock Checker's revenue is still ≥ $20k 30 days after its first renewal round, showing it isn't one-off; or if a multi-retailer alert engine hits > $10k in 30 days on indie with 3 straight months of growth. Either case moves this to "keep open".

## Evidence

Grouped by store. Each group starts with the charts that can be graphed (real curves, data dates below the chart), then the scanner's original notes and source links.

### Indie product revenue (TrustMRR)2 evidence · 1 products with curves

[Store Stock Checker](https://trustmrr.com/startup/store-stock-checker) storestockchecker.com

TrustMRR · 30-day revenue $29,252 (+0%) · MRR $29,236 · 3,829 subscriptions

Monthly revenue (verified by payment platform)

2026-10 → 2026-11 (2 pts). Light bars = current month, not yet complete

Daily revenue (UTC day)

Data 2026-09-29 → 2026-11-06 (39 days, 39 observations). Single-day swings are big, so look at the trend in the monthly breakdown above.

- Indie (US, 11-01 core): Store Stock Checker (storestockchecker.com, one person, Rust + Cloudflare, watches Apple Store stock for the [iPhone Duo](https://stringers.io/worth/p/apple.html), $5 / 10 / 20 per month) 10-23 first revenue. At time of report, 8 days $21,406, 2,798 subscriptions; 11-01 core 30 days $22,465, 2,940 subscriptions. Daily 10-28 $4,955 peaked, then $2,616 → $2,433 → $2,342; daily new subscriptions +549(10-30) → +296 → +142(11-01). 10-28 listed at $135,000 (TrustMRR).

- indie (EU / UK / US, month by month, verified by 11-01): Akari Tickets (real-time monitoring of concert and sports tickets, drop alerts, auto-buy groups) May $23,399 → July $18,775 → September $15,710 → October $13,388,30 per day $12,933 (−15.9%), 138 subscriptions, down 5 months in a row. InstantAlert (Netherlands, new-listing alerts for Vinted, €4.99–27.99 per month) May $209 → October $1,174,30 per day $1,153 (+44%), 113 subscriptions.

### App Store1 evidence items · 5 products with curves

[PokeNotify: TCG Restock Alerts](https://apps.apple.com/us/app/pokenotify-tcg-restock-alerts/id6772830132) Pokenotify LLC

App Store · launched 2026-08-10 · US store rating 858 · charted in 11-08 of 10 stores

Best category chart rank · by store

US store Canada UK

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

Ratings count · US store

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Apple doesn't publish download counts; rating growth is a proxy for downloads.

[CrownCards - Trading Cards](https://apps.apple.com/us/app/crowncards-trading-cards/id6762010774) Crown Cards LLC

App Store · launched 2026-06-03 · US rating 28,756 · 11-08 best Top Free overall rank #8 (UK) · charted in 11-08 stores 4

Top Free chart rank · by store

UK Canada

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

Best category chart rank · US store

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Best rank across each day's category charts

[TCGSniper](https://apps.apple.com/be/app/tcgsniper/id6760960120) Dynamic Software Development

App Store · launched 2026-04-19 · Netherlands rating 24 · charted in 2 stores (11-08)

Best category chart rank · by store

Netherlands Belgium

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

Ratings count · Netherlands

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Apple doesn't publish download counts; rating growth is a proxy for downloads.

[OrangeBell – Restock Alerts](https://apps.apple.com/gb/app/orangebell-restock-alerts/id6762339207) Hugo Lee

App Store · launched 2026-06-26 · Hong Kong rating 3 · charted in 7 stores (11-08)

Best category chart rank · by store

Japan Brazil UK

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

Ratings count · Hong Kong

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Apple doesn't publish download counts; rating growth is a proxy for downloads.

[Pingr - TCG & Restock Alerts](https://apps.apple.com/us/app/pingr-tcg-restock-alerts/id6778630259) EFN Group LLC

App Store · launched 2026-07-13 · US store rating 5 · charted in 11-08 of 1 stores

Best category chart rank · by store

US store Canada Vietnam

Data 2026-10-28 → 2026-11-08 (12 days, 12 observations). Lower rank is higher; gaps mean it wasn't charted that day

Ratings count · US store

Data 2026-10-30 → 2026-11-07 (9 days, 6 observations). Apple doesn't publish download counts; rating growth is a proxy for downloads.

- App Store (us, 11-02): PokeNotify: TCG Restock Alerts (6772830132,2026-08-10 debut), us Reference, free, #30,643 with 10-28 ratings (495,5 days, +148). CrownCards (6762010774, trading card marketplace) has 26,117 ratings in us, +1,840 in 5 days; gb Shopping free #10 (10-28 #5, still falling). Other restock alerts are small. TCGSniper (6760960120) charts #1 in nl Shopping but has only 23 ratings. OrangeBell (6762339207) charts #4 in tw Shopping with 3 ratings. Pingr (6778630259) has 0 ratings.

### Google Play2 evidence items · 5 products with curves

[PokeNotify: TCG Restock Alerts](https://play.google.com/store/apps/details?id=com.pokenotify.app) Pokenotify

Google Play · Launched 2026-07-24 · 11-07 installs 46,923

Global cumulative installs

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations). Google's detail page only refreshes install counts every other day, so a flat day doesn't mean nobody installed.

Ratings (total)

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations)

[PokeRestock](https://play.google.com/store/apps/details?id=com.honest.software.poke.restock.alerts) Honest Software Solutions

Google Play · Launched 2025-10-18 · 11-07 installs 11,901

Global cumulative installs

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations). Google's detail page only refreshes install counts every other day, so a flat day doesn't mean nobody installed.

Ratings (total)

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations)

[CrownCards - Trading Cards](https://play.google.com/store/apps/details?id=com.crowncards.app) CrownCards

Google Play · Launched 2026-08-19 · 11-07 installs 425,139

Global cumulative installs

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations). Google's detail page only refreshes install counts every other day, so a flat day doesn't mean nobody installed.

Ratings (total)

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations)

[Rips by Triumph](https://play.google.com/store/apps/details?id=com.triumpharcade.tcg) Triumph Labs Inc.

Google Play · Launched 2026-05-07 · 11-07 installs 1,820,853

Global cumulative installs

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations). Google's detail page only refreshes install counts every other day, so a flat day doesn't mean nobody installed.

Ratings (total)

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations)

[Rip Rush: Card Collector Arena](https://play.google.com/store/apps/details?id=com.emeraldmyth.riprush.and) Emerald Myth Studio Limited

Google Play · Launched 2026-07-01 · 11-07 installs 452,204

Global cumulative installs

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations). Google's detail page only refreshes install counts every other day, so a flat day doesn't mean nobody installed.

Ratings (total)

Data 2026-10-29 → 2026-11-07 (10 days, 10 observations)

- GP (us, 11-02): PokeNotify (com.pokenotify.app, listed 2026-07-24) 43,770 installs, us Shopping top grossing #4 (the US Shopping top grossing chart has only 18 spots, e-commerce doesn't use in-app purchase, so the bar is low); the bad reviews in the report are "$9.99 a month" and "restock data depends on users entering it themselves". PokeRestock (com.honest.software.poke.restock.alerts) 11,660 installs, us Shopping top grossing #15. CrownCards (com.crowncards.app) 10-29 346,606 → 11-02 401,766 installs.

- GP (us, 11-02): Pack-opening apps Rips by Triumph (com.triumpharcade.tcg, real-money digital card packs) 1,760,666 installs, us Entertainment free #18; Rip Rush (com.emeraldmyth.riprush.and) 448,650. This is gambling, not this opportunity; stay away.

## Already doing it

Store Stock Checker (Apple Store); PokeNotify, PokeRestock, Pingr, TCGSniper, OrangeBell (Pokémon card restock); Akari Tickets (event tickets); InstantAlert and an anonymous French deal-alert app (second-hand platform new listings, see [003]). No public revenue found for a general alert engine that works across retailers and categories.

In our product files: [iPhone Duo](https://stringers.io/worth/p/apple.html)

## The hardest step

Data sources. Each retailer's stock page has to be scraped separately, and gets blocked; and a product has to launch in the first days after a shortage starts and pick up traffic fast (Store Stock Checker's own channels were SEO, Reddit, X).

## Who it's for

Solo builders who can write scrapers and deploy fast; $5–20 per month subscriptions, start with the US and UK markets. Build it as a pipeline that adds a category within 48 hours of a new shortage event, not as a single-product site.

## Should every product builder know this?

No. But "back-in-stock alerts are event-driven, and the maker had a listing within 5 days" is a revenue shape that consumer-tool builders should know about.

## Change log

2026-11-08

Store Stock Checker 30 days $29,252, MRR $29,236. The first renewals around 11-23 are the test.

2026-11-07

Store Stock Checker 30 days $28,523, subscriptions 3,594 → 3,733 (about 70 per day). The first monthly subscriptions start renewing around 11-23.

2026-11-06

Store Stock Checker 30 days $27,476, subscriptions 3,392 → 3,594 (+202, two days' worth, about 100 per day).

2026-11-05

Store Stock Checker 30 days $25,971, subscriptions 3,326 → 3,392 (+66, daily gains keep shrinking).

2026-11-04

Store Stock Checker 30 days $25,459, subscriptions 3,185 → 3,326 (+141, daily gains are smaller again than the +200–500 of earlier days). PokeNotify (Pokémon card restock alerts) two-day ratings 59 → 78, still climbing.

2026-11-03

Store Stock Checker (the 7-day check-in on the threshold list): 30 days $24,400, subscriptions 2,940 → 3,185; daily 10-28 $4,955 → 10-29 $2,616 → 10-31 $2,342 → 11-01 $1,649, new subscriptions are falling. The value_prop wording was "Get the [iPhone Duo](https://stringers.io/worth/p/apple.html) the moment it's in stock near you", which is the Duo shortage monetizing, per [001]. 10-30 Duo expanded to 28 new stores; I didn't find anyone who has done localized versions. The first renewals around 11-23 are the key test. Status unchanged (narrowing).

2026-11-02

Backfill check: Store Stock Checker 30 days $21,406 → $22,465, subscriptions 2,798 → 2,940; after the daily peak on 10-28, it ran 3 straight days at $2.3–2.6k, daily new subscriptions fell from +549 to +142, so the peak of restock demand is probably over. Akari Tickets has fallen 5 straight months. PokeNotify App Store rating 619 → 643; CrownCards GP installs 369k → 402k, and the Pokémon card wave hasn't faded yet.

2026-11-01

First record (backfill: from Revenue Library "Recently started earning" §1.2, App Store New Opportunities §1.7, Google Play New Opportunities §1.10, Stringers §3.3; data as of 2026-11-01).

Original: Scanner opportunity library #037 (updated daily, 06:00); this page was generated on the 2026-11-08 edition.