A long time ago I used to use BugTrapper - an application that sits on the production server, records every instruction, and makes it possible to "play" everything back, step by step. It's a great tool to analyze bugs and especially crashes "post mortem", as long as it's not related to some obscure race condition (the overhead of using BugTrapper often ruling out the race in the first place).
I think there definitely is a case for applications like this, and the fact that Mutek hasn't been able to push itself farther into developers' awareness is quite surprising to me.
The feature I would like to see in an IDE is a mini-BugTrapper. I would like the IDE to be able to record up to a certain amount of instructions (say up to 100,000) during debugging. How many times did you stop at some breakpoint and suddenly realized you should have put this breakpoint a little bit earlier in the flow? You really need to see the value of some parameter, or the actually executed flow, a few steps back - but you can't. The only thing the IDE gives you is the static current call stack - which just isn't enough. You want to know what variables caused you to get into that current call stack, but that's beyond the scope of the IDE's features.That's, IMHO, a killing feature that could significantly boost debugging time.