I hear that CHIP-8, XPL0, PicoC, and Objective Caml have been ported to graphing calculators.
The Wikipedia "Lego Mindstorms" article lists a bunch of programming languages that allegedly run on the Lego RCX or Lego NXT platform.
Do any of them meet your "live coding" criteria?
You might want to check out the other microcontroller Forths at the Forth wiki . It lists at least 4 Forths for the Atmel AVR: amforth (which you already mention), PFAVR, avrforth, and ByteForth.
(Links to those interpreters, as well as this StackOverflow question, are included in the "Embedded Systems" wikibook).