Comment My phone already does this. (Score 1) 151
A few months ago I left work to run some errands and stuck my Android phone in its car charging dock (which automatically activated my preferred nav program). Six or seven miles down the road I noticed the icon representing my car was different than normal and my location was about a half-block off my actual position. At the next stoplight I checked and discovered my GPS was turned off. My phone had reasonably calculated my position through several turns and stops using only the accelerometer (dead-reckoning). At the time I was impressed.