How store reminders actually work

Most apps that offer this explain nothing. Here is what your phone is really doing, including the parts that are limitations.

Your phone is not tracking you

When you pin a shop, the app hands the operating system a circle — a point and a radius — and asks to be woken if you enter it. That is a geofence. iOS and Android both have hardware-assisted support for this, which is why it costs very little battery: nothing is polling GPS, and the app is not running in the background watching you move.

No coordinates ever leave your device. When an alert goes to the rest of your household, what travels is the fact that someone is near a named shop with a number of items outstanding — not anyone’s position.

Why it works with the app closed

This is where most implementations quietly fail. If the notification is built in the app’s web layer, a force-quit means there is nothing left to build it, and the alert never comes.

Home List posts the notification from native code in the OS callback itself, so the app does not need to be alive. We tested this the only way that counts — force-quit the app, drive to the shop, and confirm afterwards that no server request had been made when the notification fired. It had not. The phone did it alone.

The limitations, stated plainly

Detection is not instant. The OS trades precision for battery and typically notices you have entered a region within a few minutes, which is why the radius is adjustable from 500 feet up to 10 miles — a bigger circle buys earlier warning.

It needs background location permission, which is a real thing to grant and you should grant it deliberately. On Android, aggressive battery optimisation can delay or suppress the wake-up, and the app will tell you when it detects that.

It cannot work in a browser. No web API can register a geofence, so arrival alerts are phone-app only.

Turning it off

Alerts are per shop, so you can keep one and silence another. Telling the rest of the household is off until you switch it on, and there is a cooldown so lingering near a shop does not produce a stream of notifications.