TMO features a 16x16 LED display, simple input controls and a (not yet implemented) variable frequency square wave sound generator. The non-Teensy hardware is all designed from scratch, as is the simple operating system providing an interface to the system and gave development API. I was inspired to build TMO by the character BMO from Adventure Time, whom I modeled my devices appearance from.
See amazing LED project here: http://kck.st/1Oi2sHC
Simply and affordable...