I'm going to hope that you don't need to buy an entire PS3 in order to buy a PS3 controller.
Axim serial pin out is here:
http://www.aximsite.com/boards/showthread.php?t=29804
Example software of how to monitor Windows Mobile hardware button inputs is here:
http://msdn.microsoft.com/library/de...PInvokeLib.asp
The Axim x50v doesn't have USB host capabilities, only USB client.