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 and Poly modes
• High-note and low-note priority modes
• Assign to any MIDI channel or Omni
• Pause mode ensures that first note is released before next is played
• Board dimensions: 1.04″ x .4″
• Power supply: 3.3v-5v
• Includes 2.5mm phone jack for mounting in small devices

Includes:

• Midify board
• 2.5mm phone jack
• MIDI cable (2.5mm pone plug to standard MIDI plug)
• Double-sided tape
• 30AWG wiring kit