This is neat. Way beyond me. But very neat.
NoICE is a debugger for software written on the 6809 (actually, for many microprocessors). It runs on a PC with a little driver on the target system. A serial cable hooks the two together. Then, as your program runs on the CoCo, the NoICE is acting as a debugger on the PC. Again, no idea how to make it work, but all the tech stuff is there to build the driver (OS-9, ECB?) and cable. If you're doing assembly on a CoCo this might be a great package to look into. And apparently the developer is a 6809 fan, so the 6809 version is Free! :)
Addendum: I just read a thread on the maltedmedia list (Vol 31, N. 18 roughly, search for noice) from the hi tech guys in there. They go into a lot more detail and idea for using NoIce. Check it out.