Tile
While no one has quite managed to invent Google for real life just yet, Tile at least takes us a step closer towards answering the question “where did I leave my keys?”. Simply attach this tiny bluetooth slab to your keychain, your wallet or your dog and when they go missing, you can use the app on your phone to hunt them down by triggering it to play a tune. It even works in reverse - so if you lose your phone, but have your tile on your keyring, you can make your phone shout instead.
What's also clever is that if Tile becomes ubiquitous, it will work even better as when you run the Tile app it will also pick up other Tile devices within range, even if they don't belong to you - and will securely report their position back to the rightful owner (without revealing any of your details).