With Guitar Prodigy, you have a tablature that scrolls across the screen and you play the notes as they come across the play bar, and you score points when you hit the correct note. It uses the bulit-in microphone on the iPad, or you can use one of those adapters where you can plug an instrument cable into the earphone jack.
If you register at the website, you can download several free lessons plus one song, "Bad Moon Rising". There are four levels of difficulty. plus a practice mode where the scrolling tablature will pause until you hit the right note.
The software does have a few bugs. On my iPad the toggle between practice and perform mode does not work, although I have found a workaround for that by selecting the auto-pause button; this automatically puts you into practice mode. Sometimes the auto-pause does not pause when it's supposed to, and I am haunted by the occasional crash. However, the bugs are not so bad as to make it unusable.
Yoiu can purchase additional songs and lessons. Songs tyically run $1.99. The library is limited to maybe 30-40 songs but there is a lot of variety among them.
Just wondering if anyone else has tried it and what your impressions are. There is a lesson on the chromatic scale that I find to be a great warm-up. It is very much along the lines of the warm-up exercises David has in the Complete Idiot's Guide to Guitar, and I now find myself using this tool to start my practice sessions.
"Growing Older But Not UP!"