I suspect a lot of these devices use the Analog Devices accelerometer. I have never cracked open an OQO or iPhone to check though :-) I wouldn't be at all surprised if they use the same underlying sensor. At one point Microsoft had a game controller that used it - you could tilt to control motorcycle racing, etc. I think it was called the Sidewinder Freestyle Pro.
The Analog Devices accelerometer is a MEMS based technology. You can think of it as a little see-saw that tips depending on how the device is tilted. The height of the seesaw changes the distance between two plates so you have a change in capacitance, which can be sensed very precisely. These have been around for quite a while. I used the ADXL202 two-axis linear accelerometer in my old days of sensor hacking (almost 10 years ago now!), but I'm sure they have newer versions now. Three axis accelerometers are now available as well. There is also a company called Kionex that makes accelerometers.
Hey Ken,
Thanks for explaining how the accelerometre technology works.
Stu
