When the project is done, each of our bikes will have wooden enclosure control panels mounted in the center of the handlebars. There will be a few status LEDs, a large arrow and 4 buttons: "Call", "Seek", "Home" and "Cancel". At all times both control panels will be announcing their GPS location to the other bike via long range xbee.
The Call button broadcasts a simple 1 bit call message to the other bike to come find you. This causes the call LED on that person's bike to start flashing and a noise to sound.
The Seek button will immediately guide you to the other bike via the large arrow that is mounted to a motor via a long spring coming out of the top of the control panel. A 1 bit seek message will be sent to the other bike to let them know you're coming.
The Home button will direct you back to camp from wherever you are.
The Cancel button will cancel any of those three button actions.
Each control panel will be communicating via XBee-Pro 900 XSC S3B, which have about a 9 mile range...line of sight. Burning Man is flat, however, there are many camps, RVs and design installations that might get in the way. I'm not entirely sure how this will interact with the signal. To compensate, I'm considering putting an XBee repeater on a mast above my camp to boost the signals from each bike.