A tiny Bluetooth BLE module, on an equally tiny budget. The BOM of this module is below $1, and about $0.5 in large quantities.

The use cases of this beacon are plenty, from standalone lost item finders like key trackers, but also firmware to join the various global FindMy networks is available. The temperature sensor in the CH591D MCU can be used to create thermometers that advertise over BLE with multi year battery life on a CR2032.

Due to the size it can be tucked away basically everywhere there is 3v available, like power tool batteries or the door lock slot to indicate if the door is locked or not. The extreme dimensions even allow it to be carried by a toy helium balloon so it can be tracked after it lands! When used with FindMy firmware it can be added to all kinds of portable electronics, bike light, scooter/ebike electric system or boat or car to enable finding back a lost / stolen item.

The low BOM cost even allows it as a backup tracking solution for shipping expensive items and locating lost luggage on vacation of all bagage items, not just the big suitcase. So plenty of uses for a disposable beacon like this, and I'm sure others come up with creative applications too!