Researchers at the VTT Technical Research Centre of Finland have developed a prototype of a cell phone that uses motion sensors to record a user's walking pattern of movement, or gait. The device then periodically checks to see that it is still in the possession of its legitimate owner, by measuring the current stride and comparing it against that stored in its memory.
Gait analysis is an established "biometric" method for identifying a person. It normally involves analysing video footage of a subject as they walk past a camera and is generally less reliable than fingerprint or iris analysis.
Ailisto says, using the simple motion sensing gait method, the prototype phone correctly identified when it was being carried by someone other than its owner 98% of the time. It also only triggered accidentally, when it was with its rightful owner, 4% of the time.
If it decides it's not with its rightful owner, it prompts the user for a password before allowing a phone call or access to memory. At least it doesn't explode or something. Having your customers die in flaming agony because of a false alarm would be bad for business.