There is, and its built into Exec. Its called SAD, and its a built-in debugger. You can access it via a serial connection (9600BPS, IIRC). Details are in the exec.library autodoc.
Be warned: it is very technical, and you have to know your assembler, and the Amiga's workings.
As for something more user-friendly... well... i'm not sure anything really useful is possible.
