Dance Dance Revolution is great. If you like dancing. If not, its applications are somewhat limited. Note we say somewhat, though, and not totally, as you can still use it to drive... Windows Media Centre.
Why you'd do this, we don't know. Unless you had no arms, or something. It could at least have some back-up dancing and maybe some kind of highland jig. Or be put to use on something a little more interesting. Like a game. But still, seeing two DDR dancemats (for the PS2, no less) stitched together and made to do something practical is worth a "well done" and a pat on the head.