You can get a PID by forking the pid.codes repo, claiming a PID, and sending a pull request. Once that’s accepted, that PID is yours forever.

One will generate the a PID code based on your Kindle's serial number, which can then be used at sites such as Fictionwise to buy books that will then be accepted by the Kindle.

They work in conjunction with a gyroscopic sensor and PID code to keep the two-wheeled platform upright. An mbed board running 96 MHz provides plenty of computing power for the balancing system.