Sentinel: sold out, until it isn't

Anyone who has tried to buy a booster box, a limited figure, or a restocked pair of anything knows the routine. The page says sold out. You refresh it. You refresh it again tomorrow. The one time it comes back, it’s gone again before you see it. Sentinel exists because refreshing a product page by hand is a job for a computer, not for a person.

You add a product link once. Sentinel keeps checking it in the background, on a schedule you choose, and the moment the page changes it tells you: a desktop alert, a Discord message, or a webhook to anything you like. A drop goes live, a size comes back, a reservation opens up — you hear about it seconds later, not hours.

It works where the drops actually happen: Walmart, Target, Best Buy, Amazon, Premium Bandai, Hot Topic, Crunchyroll, Shopify stores, even OpenTable reservations. Each store is a plugin, and new ones arrive in the app without a reinstall.

It runs on your computer. Sentinel does its checking from your own machine, not from a server somewhere, and your store logins stay on your machine too.

One honest caveat: this is a public beta. Expect frequent updates (the app installs them itself), and expect to find the occasional rough edge.

Sentinel runs on macOS (Apple silicon) and Windows. Grab the beta at sentineldrops.com.