Internal Kernel Debugger
An Internal Kernel Debugger will allow you to view data inside core structures, like memory, tasking, and other structures. It is very helpful.
The idea is that you get dumped into a mini shell. You will need a keyboard driver. You then have some commands, like to dump the registers, read a structure, and so on. The difficult part is going to be keeping the structure of an operating system, and allow it see the guts of other components.