Such a simple device – the Tile Tracker.
This is a small bluetooth tracker which you can attach to your keys/bag/camera/car etc. This is then paired with an app on your phone to use your GPS and record it’s location.
If you can’t find your tile, you fire up the app and make your tile make a noise. If you lose your phone, you can press the button on your tile to make your phone make a noise (even if it’s on silent).
What if you loose your item and tile further away – out of range of your phone? As soon as ANY tile user gets within range of your tile – it’s location will be recorded.