I haven't used the one on the iPhone, but search for "ballistics" with the Android Market app.
I have a HTC Hero, which has an older OS than the Droid; I have been testing out two programs - "Ballistics", and "Shooter Lite". There's also a pay version called "Shooter" that has more options. I just started trying these out so I don't have a lot of experience with them yet. Hope this helps a little!