This looks really neat! There was a story about Lisp at JPL that got me dreaming about embedded REPLs:

> The Remote Agent software, running on a custom port of Harlequin Common Lisp, flew aboard Deep Space 1 (DS1), the first mission of NASA's New Millennium program. Remote Agent controlled DS1 for two days in May of 1999. During that time we were able to debug and fix a race condition that had not shown up during ground testing. (Debugging a program running on a $100M piece of hardware that is 100 million miles away is an interesting experience. Having a read-eval-print loop running on the spacecraft proved invaluable in finding and fixing the problem.) http://www.flownet.com/gat/jpl-lisp.html

So often in embedded development I resort to things that make printf-style debugging look downright virtuous. ("If you reach some complicated runtime state, blink the LED thrice.") Having a REPL would let you poke around without the compile-flash-test cycle and have an actual conversation with the hardware.