Hi, This is my PICAXE 20m2 based car. It is controlled wirelessly by an android phone with the help of a bluetooth headset.
An android application plays four different audio frequencies (500 Hz, 1000 Hz, 2000 Hz and 3000 Hz) which comes out from the bluetooth headset's speaker port, these audio signals are then fed to an Op Amp which amplifies them and sends them to picaxe which do functions accordingly.
I am using the count and select commands on picaxe so it counts the pulses coming on b.7 pin and responds as programmed to :)
The audio signals coming out of the BT headset's speaker port are analog and are at a very low voltage (less than 1 volt which picaxe can't count) so i have used an Op Amp (LM358) which converts them to digital pulses at 5 volts! :D
I made a custom picaxe board using a perf board and it has a PICAXE 20m2, a ULN2803 and a L293d motor driver chip all on the same board!
Here is more info about my board if you want- http://letsmakerobots.com/node/32986