Hm, it would be cool though, if we could achieve some sort of piping system for graphical applications.
Would be really cool, though.
A potentially easier idea I have ruminated on is just letting apps (or better, having the OS almost force them to) expose a "current app environment state" that any other (authorized) app could read and subscribe to (in some waves hands efficient way).
Even in this example, though, you already have security concerns: do I want other apps to be able to know that my file browser is perusing the "pr0n" directory? If no, then how do we put the user in charge of that kind of thing in a way that is simple enough not to make the entire idea more trouble than it's worth?