See, it's like this super-techy, Bluetooth-y version of the beeping thing that helps you find your car in the parking lot.
The Nokia Locate Sensor is a tiny gadget which works via an application downloaded to your phone. Simply attach it to the object you tend to lose - keys, wallet, your head if it wasn't attached to your body - and start the app on your smartphone. Leave it running in the background, and if you drop the item with the attached Sensor, the app will notify you and guide you to the lost object as long as it's within a 100-metre radius.
The application can remember up to 100 different tags, so you can keep an eye on practically everything you own. (Of course, you'd also need up to 100 different Locate Sensors.)
The Nokia Locate Sensor is still a prototype - it was unveiled at CES 2009 - and there's a number of unrevealed details, like the actual technology involved (it's not GPS, but may be Bluetooth or Wi-Fi, according to GSM Arena).