Is there a way to set application-specific 'hot corners' in OS X? OS X's 'hot corners' feature is great, but I'd like to use it in just one specific application - or, set a specific hot corner action for one app, and a different action (for the same corner) in another app.

Is there a tool that can do this?

The tool CornerClick seems to have a lot of custom features over OS X's own one, but from a brief look it doesn't seem it offers a way to actually isolate/customize hot corners to specific apps per se.
CornerClick and AppleScript

Try creating an AppleScript that is triggered by CornerClick. Your AppleScript could check which application is front most and act accordingly.

Enhancement Request

Also, consider opening an enhancement request with CornerClick. The project is open source and your interest may help motivate the author, or other developers, to improve the product.