Division 6 is shipping Midify, a tiny board that can add a MIDI port to just about anything. 
It’s $35, and can be installed directly into a GBA, GBA-SP, DS or DS Lite, or with some extra parts you can interface it with other devices.
 
Features:

12 outputs
Outputs can be active-high or active-low
Map any MIDI note to any output
Mono [...]

Limor Fried, creator of the very cool x0xb0x 303 DIY project, has released MIDIsense, described as “a simple, yet extensible sensor interface system for artists, musicians and others interested in experimenting with sensors.”
The MIDIsense boards provide a simple way to integrate various common sensors with existing software such as Max/MSP, Ableton Live, etc. or directly [...]