Just got an android phone, that's Google's new operating system. The app I downloaded for it uses the built in gps to tell you current speed and alarm for when you exceed set speed. Also has trip information like miles traveled, travel time, min max speed, average speed,0-60 and 1/4mile.
Also saw someone wrote a program that uses a blue tooth adapter to read obdII port. Has the possibility to be better then the ScanGauge or Ultragauge only limited by software written for it, plus with 1ghz processor it can do a little more then the ScanGauge/Ultragauge.