Locking the Chirp GPS app gives you the ability to create a pin code to access any features of the app. This is often used with fleets who just want to keep Chirp running, or with unruly children. When Chirp is locked, the only part of the app that continues to work is the background GPS sending of a users location, and the panic alerts.
To lock Chirp, go to the settings screen, tap lock, then set a pin code. To unlock, use the same pin code you entered. Be warned though, if you set a pin and do not remember it, we cannot help you, so please write down the pin you set.