Bluetooth to MIDI is coming along nicely at this project.

Here’s a summary at Hack-A-Day (with 2 videos) and here’s part 8 of Peter Brinkmann’s writeup. (Other parts are available.) You’ll need a (hackable) Android (not iOS) for this simple-to-breadboard interface. Sounds like kits will be available soon.

Here’s a recent CDM post on the topic, with a link to the free software.

Bonus unrelated hardware project: ◊Rockit 8-bit open source synth