>You CERTAINLY don't want someone to be able to make your car segfault while you're driving down the highway. That could make for a great scene in some futuris

>You CERTAINLY don't want someone to be able to make your car segfault while you're driving down the highway. That could make for a great scene in some futuristic hacker movie. On a more serious note, there are many possible solutions to the problem of losing a wireless car entry key. Off the top of my head: 1) Have the user tap out a simple rhythm with the button to unlock the car. Downsides: kind of involved and the rhythm would have to be long to be secure. 2) Put a fingerprint scanner on the key. The one in my laptop is a tiny self-contained module, so I expect it to be possible to fit one inside a wireless car key. Downsides: the scanner can break; can't use in gloves. 3) Have the cars mesh network to detect the "trawling for the right car with a key" behavior. Downsides: complexity; the thief could exploit this to lock you out of your own car. 4) Make the key a wristwatch or a wristband. I think this is the best cheap solution. Downsides: might disagree with your fashion sense.