This is perhaps far-fetched, but what's this thread for if not spinning ideas out of thin air...
I was playing my bass guitar the other night and thought, it would be great to have an Elektron box that was kind of like the Heat (a couple of flavors of overdrive), with a multimode analog filter, possibly some other functions (envelope follower, digital effects?), with Elektron's sequencer and 16 buttons to program parameter locks.
It wouldn't create any of its own sounds, but you could build p-lock sequences to effect the audio you were playing through it (say a mono synth or bass guitar).
Of course it could be synced by MIDI to the tempo of a track, but the interesting thought was this: could they build a device that instead of running at a set MIDI tempo followed the tempo of the live playing to control the sequencer? If you could have two modes -- in one it'd set a tempo at a chosen time signature by trying to extract that tempo from the playing, and run the sequencer as we normally expect. In the alternative mode, the sequencer would advance with each note you played, regardless of any sense of "tempo" (so if you played two whole notes the sequence would move two steps, then if you played 8 16th notes, the sequence would move forward another 8 steps).
It'd have a threshold control like the envelope follower on the Heat for controlling the sensitivity of this detector. And also a side chain input so you could pick up the tempo from a kick drum, say, while affected the audio from a monosynth or bass guitar.