If you look around on Google, you will also find an app for blackberry (I don’t think it is for the Ipod) that functions as a sound driven chronometer. It listens for the initial boom and the corresponding hit in the paper target and calculates the velocity by sound. Cool. Not sure what the name is...
Sounds like something I could use. If you find the link, please post it.
For you IDPA/IPSC types, there’s also a company that sells shot timer software for smart phones. Don’t recall the name at the moment.