I've recently been playing a lot of WarioWare Twisted! for the GBA.
It uses a gyro sensor for controlling dozens of minigames. Here is a
video I made(with help from Gordon) of the globe minigame. I think it
demonstrates the incredible granularity of the sensor.

http://blog.ronin64.com/files/MVI_2637.AVI

What this example does not convey is the subtle vibration that the
minigame use for feedback. Each time a different continent is
selected by twisting the sensor, the game pulses a quiet rumble motor.
I think adding rumble feedback and one or more gyro sensors to a
chord keyboard could increase the amount of control available.

According to http://www.devrs.com/gba/ the sensor is
http://www.nec-tokin.com/english/product/piezodevice2/ceramicgyro.html

There are many who believe the controller(s) for the Nintendo
Revolution will contain 1 or more gyro sensors.