I think something like this would benefit Ruby & Rails development a huge amount. I miss the capacities the Smalltalk (+Self) browsers enabled the facilitation of.
The disadvantage was that it was an "entire closed world" but this is a more open idea... also it seems to integrate with Eclipse, which may mean RadRails would integrate with it. Would this mean we could browse class hierarchies of Ruby and directly execute code, etc?
It'd be fantastic if this was the case. A dream come true.
http://www.cs.brown.edu/people/acb/codebubbles_site.htm
Julian.