Hello MMDers,  I've developed and built a system of MIDI wireless
using the Arduino microcontrollers and 915 MHz radios.

It is a one-way, one-to-one link between a MIDI player (a computer
or laptop MIDI file player) and a MIDI instrument like a player
piano or organ.  It requires less than $50 in components.

If anyone wants to try the implementation, I can give some support.
It was already done by some.  More information about the hardware and
software is here: http://forum.arduino.cc/index.php?topic=253382.0 
Vimeo video: https://vimeo.com/99947862 

Wagner Mello

 [ A schematic diagram of the microcontroller plus radio is at
 [ http://www.anarduino.com/miniwireless/#schematic  -- Robbie