I like the concept... 
via Gizmodo by Mark Wilson on 3/26/09
Scenario: You're walking down a dark alley when you get jumped. Someone grabs your bag. They get away. Your nose is broken, ribs bruised. That is, until an alarm goes off in your pocket.
If the blood gushing down your face weren't enough, the Nio, which measures proximity to your connected Bluetooth devices, confirms that your cellphone has indeed been stolen. As the high pitched squeal adds the cherry on top to your excruciating head pain, all you can think is, thank goodness I spent $50 on the thing. Now I know for certain that I cannot call an ambulance. [Nio via Engadget]