GWS PG-03 Piezo Gyro. This tiny gyro is about 1" square and weighs less than 0.3 oz! Piezo gyros can be used in robotics for balancing, or to detect rotation, or to drive a "tracking" servo which continues to point to a fixed object even if your robot turns.

A Piezo Gyro senses rotation about a single axis and outputs a servo signal intended to be used to counter that rotation. Piezo gyros are typically used in R/C aircraft to stabilize flight by automaticaly countering unwanted motion, e.g. from wind. They can also be used in robotics for balancing, or to detect rotation, or to drive a "tracking" servo which continues to point to a fixed object even if your robot turns.

Extremely small and light, this gyro can be used on almost any sized robot. Comes with universal 3-pin connectors, for compatibility with all brands of servos and radio gear.

Datasheet
Examples of Gyro Usage (.pdf 303 Kb)