Yamaha has announced a product called Bodibeat, a music player which will adjust the tempo of the music to follow your walking or running. It is based on an accelerometer and, I guess, an algorithm detecting peaks in the continuous movement signal. This gives the pace of the walker or runner which again can be used to control the playback speed of a music file. Apparently, the technology is based on research by BMAT, which is a spinoff from UPF.
I am curious to see/read/hear more about how the implementation is actually done, e.g. how quick the update time is. To prevent pitch changes I assume they use a phase vocoder to time stretch the audio, but how do they handle cases where the person does not move. Anyway, I am sure this is just the first of many future products that will explore the relationships between body movement and musical sound. Apple and Nike teamed up and released an elegant solution for movement detection last year, but so far this is just an expensive pedometer. Now as Yamaha is releasing the Bodibeat they will probably push forward and release some more interesting applications very soon.