If you have not seen/used/heard of the Korg Kaoss pad then I highly recommend checking one out. The touch-sensitive pad can be used to control synth elements as well as pitch, filters, delays, granuler stuff (stuttering) and other effects. The feature I enjoy the most is the sampler, which allows you to quickly build a looping groove using the built-in sounds or an external mic/line source. There is a lit tap-tempo button which pulses to the selected tempo, allowing you to perform a loop that fits perfectly to the tempo map (although the flashing light-metronome makes it hard to judge so it takes a bit of practice).
Overall, it's pretty fun but not something I would rely on. It's a bit difficult to keep with the tempo mapping because of the flashing light and because there is nothing to indicate when a given sample starts over. It's fun, but not worth my $400.