Technology review has a short article on new work on doing gait analysis with the accelerometers built into many smart phones, Smart Phones that Know Their Users by How They Walk. The results are from the following paper:

Mohammad O. Derawi, Claudia Nickel, Patrick Bours and Christoph Busch, Unobtrusive User-Authentication on Mobile Phones using Biometric Gait Recognition, The Sixth International Conference on Intelligent Information Hiding and Multimedia Signal Processing, Darmstadt, 15-17 October 2010.

Abstract: The need for more security on mobile devices is increasing with new functionalities and features made available. To improve the device security we propose gait recognition as a protection mechanism. Unlike previous work on gait recognition, which was based on the use of video sources, floor sensors or dedicated high-grade accelerometers, this paper reports the performance when the data is collected with a commercially available mobile device containing low-grade accelerometers. To be more specific, the used mobile device is the Google G1 phone containing the AK8976A embedded accelerometer sensor. The mobile device was placed at the hip on each volunteer to collect gait data. Preproccesing, cycle detection and recognition-analysis were applied to the acceleration signal. The performance of the system was evaluated having 51 volunteers and resulted in an equal error rate (EER) of 20%.

The potential application is that a phone could recognize that it may have been stolen if it is being carried by a person with a different gait. I guess it would then phone home with it’s location, not unlike the golden harp in some version of Jack in the Beanstalk.

The accuracy would have to be improved to make this practical, of course, and it might not be a killer app, but it is a good example of how passive sensing by smart phones can acquire useful context information.