how to access a cell phone transmitter (emergency, GPS, document)

[quanchuynh]

I have a small project to build a simple app on smart phone. In cases of emergency, the app accesses physical layer of the phone transmitter and starts sending SOS message along with its GPS position. This message can be picked up by nearby mobile receivers (e.g. other smart phones, no cell tower available). Is it possible to access physical layer that controls the transmitter? If so please point me to documentations.