Originally Posted by colnelb
To add to my previous comment. Before there was GPS, there was "inertial guidance systems" (IGS) that were used to navigate by. IGS used a combination of accelerometers and gyros. The gyro would allow you to calculate which direction you were going and the accelerometers would allow you to calculate how far you have gone. At the time, IGS was the most accurate navigation system available. If properly set up, a good IGS could show you within a short distance where you were and what your altitude was. They continue to be used as backup navigation systems for some things.
I used to work on those, up to the ring-laser gyro models.
Actually, the gyros had pick-ups on them that essentially provided raw accelerometer counts. Remember basic calculus - 1st derivative is velocity, 2nd is acceleration - so in reverse order - integrate accelerometer data once for velocity, integrate again for position change.
I'd not want to use any phone for inertial nav tho - the iPhone would require iTunes for some part of it, and the Evo would be displaying ads for businesses you were passing by. (j/k lol)
But - there's a lot of interesting games and apps that can benefit from a gyro, no doubt.
Glad you brought up MEMS. Here's a view of a MEMS gyro for those interested - iPhone 4 Gyroscope Teardown - iFixit
Here's an interesting Apple vid - it has Jobs doing the demo, so if anyone doesn't like him, don't watch -
YouTube - Apple iPhone 4 Gyroscope demo