Wow, not sure how I missed this one – the Bliptronic 5000, a relatively low-cost (aka hackable) melody grid sequencer from ThinkGeek. The 50-dollar device sports 8 casio-esque voices, tempo control, and can be linked up with additional units to play longer sequences. CDM posted an interview with product dev Ty Liotta revealing a very awesome early prototype version –
The switches were intended to be a cost-saving measure, but the engineers figured out that it was actually a little bit cheaper to use LEDs and the plastic buttons. The sounds come from a standard Casio-type FM synth chip, which is controlled by the onboard sequencer/logic chip. The Bliptronic can be chained together with other units to form longer sequences via the sync jack on the side, which operates via voltage pulses.
More of the story over at Create Digital Music