I've just come across
C64 Debugger which is a realtime C64 debugger. This video
[ Show youtube player ] details a lot of its features.
It's never occurred to me to debug in realtime but it would be extremely handy! I imagine training, development, graphics ripping, etc. would all benefit because you can see where things happen at a given moment. Unreal!
This isn't exactly a "UAE Wishlist" post because I don't expect to see this in UAE itself, but more of a curiosity if it exists, perhaps is in development or has even been discussed before. (EDIT: For that reason, maybe a mod can move it to support.WinUAE or similar?)