Ploytec, the German makers of ultra small footprint synthesizers, has introduced a new variation of this concept: the Pi L Squared Leukos synth.
It works with a computer or iPad (camera connection kit required) when attached via USB to its micro-USB connector. It also features an additional individual MIDI output.
Here’s a video introduction to the PI L Squared Leukos synthesizer:
See the Ploytec synth product page for details.