Meet Chipolo: a Bluetooth device that lets you track and find your keys, wallet, and laptop. It is about the size of a coin and works with iOS, Android, and Windows devices. The replaceable battery lasts up to 6 months.
Chipolo can be used to locate your wallet, keys, handbag, and other personal items. You can also use it with your smartphone camera to take a selfie. Costs under $30 at this time.