After you buy MP4 videos that contain the song and a video lyrics that are highlighted as they should be sung (sorry, no bouncing ball), you import them into iTunes, which can then sync them onto your iPod.
My first concern was that the catalog would be anemic or entirely foreign, but neither appears to be the case. Currently, the Rock section alone lists over 1500 songs, and you can request that songs be added if you can't find what you're looking for. $229 seems like way too much to spend to do karaoke on the MusicJam, especially if you don't even get a file that already contains lyrics, but NoPi's hardware-free, low-barrier-to-entry approach makes a lot more sense.
