Alessandro Lambardi created a tool aimed at improving the piano keyboard self-teaching experience with direct interaction between the student and software (or human, remote) teacher.
The new level of interaction is reached when the student is guided on the notes to play or exercise on visually with LEDs placed directly on top of the piano keys. A Personal Computer running music-teaching software or regular score composing/playing software (Sonar, Cakewalk, Sibelius, Rosegarden,..) is connected trough its MIDI out port to the MIDI in port of the ‘MIDI Piano Instructor’. Optionally the MIDI through port of the MIDI instructor can be connected to the MIDI in port of the electronic keyboard or piano. The same MIDI messages that play the music or the exercises on the piano, light up the LEDs on top of the piano keys. The student replicates the exercises watching directly the keyboard without diverting attention from the piano keyboard to look at the PC screen.
The result is very professional and looks like it was a part of the piano, excellent work and a helpfull application combined together.
Complete documentation, schematics and all the info you need can be found here.