Atmel based MIDI data analyzer –

The MIDI Viewport is a data analyzer for MIDI messages. But it is also much more. Handheld, battery powered, and compact, it displays MIDI data in the order it is received, one byte at a time–using an LCD 2 line by 16 character display. Connected to a keyboard or sequencer it will tell you, in English, which MIDI events are being sent by the device. You can scroll through the 64-byte buffer to see what is really going on in your MIDI system.

The MIDI Viewport – Link.