OK I tested shortcutd again and it works

?

right with the battery drain, but I can't put it in hildon-desktop in a clean way (by now, in no way). I don't know how much power an application uses which tracks all movements all the time calculates, compares...
I would say you always need some trigger. As the desktop has only left/right swipes, it's easy to replace them. But pannable windows, games, text edditing needs a lot of black/whitelisting
Swipe from bezel is ugly .
If you can realize that academic stuff, you're welcome

Maybe you've proven me all wrong in your text, but please : shorter!