It's a super neat gem. Improving error pages is always a good idea, I'm actually really happy with the relatively minor changes we added in 4.0, so I could totally see this or something like it, thanks.
I always wished Exceptions captured variable values so I could log them and not have to reproduce a bug in order to see what happened. To that end, I made https://github.com/ericbeland/exception_details. Perhaps Rails exception logging could include logging variable values at exception-time?
