Not a scheme, but for running a lisp on microcontrollers uLisp is pretty amazing. http://www.ulisp.com/
You even get a REPL and everything WHILE running on the hardware. Super easy to set up and get going. Though as it is interpreted so you will of course not have native performance. Still very useful for prototyping and hobbyist projects.
As a rule, interpreted code has a smaller memory footprint than natively compiled programs.
Even interpreted on a several hundred MHz classic RISC microcontroller, Lisp will chew through a million cons cells a second or more - an order of magnitude or so faster than the old Lisp machines in the 80s were and they used to run giant CAD systems on those to design aircraft and stuff. (Albeit slowly...)
OTOH if you want something that gives you a REPL and everything directly on the hardware but is also not as slow as your typical interpreter, look at Forth.
You even get a REPL and everything WHILE running on the hardware. Super easy to set up and get going. Though as it is interpreted so you will of course not have native performance. Still very useful for prototyping and hobbyist projects.