Race Buddy - How fast are you? app for iPhone and iPad
Race buddy helps you to measure acceleration from a standstill or while you are rolling. It has the ability to record video and overlay all your data (speed, temperature, G-force, the difference in altitude, etc) over your video and you can share it with your friends.
Supported external bluetooth devices are: RaceHF Bean, Racelogic VBox Sport, Dragy, and RaceBox.cc