I wonder if there's anybody left in Scheme land ( put away your knife, I know there is) other than the scattered remnants of the Rice PLT group? Still, these guys do good stuff. Sometimes the hammer guy can get pretty ingenious turning the world into nails.
Shriram Krisnamurthi's team at Brown University has put together a toolbox for program monitoring called MzTake. Pitched as a debugging tool, they've devised some primitives for announcing program events, and a domain specific language, FrTime, for reading and reacting to those events. FrTime can alter program execution.
Forget debugging!! This is an open extensibility mechanism. Imagine your browser or aggregator instrumented with a set of events, including UI behavior, that can be externally monitored within a convenient programming environment. All sorts of gluing and mayhem would ensue. Infrastructure like AppleScript and COM sort of support this, but they skimp on the event driven end of things acknowledging the fact that help is needed from the applications to start with.
Seriously, what if every application was written with MzTake style applications in mind? It might not be that far fetched in a world where logging is growing more popular.
Hat tip to Lambda the Ultimate.