[Mark McLeod]

I didn't quite remember correctly. The board uses a built-in accelerometer to detect motion rather than a gyroscope, but it's pretty good.
There are example projects that comes with the PSoC Programmer showing how the output is accessed and used.

I don't remember the accelerometer being passed through the FRC WPILIB API though, so if you are planning to use this through the Driver Station application, then wiring your own gyro in may be the way to go.
Ask in the Java subforum.

Depending on how you plan to integrate and use the PSoC you may not need the FRC firmware. For instance, it can be used directly by your own program running on a laptop instead of coming in through the Driver Station.