Systemwide would be better, but you'll have to consider scrolled windows, text editing or drawing apps and all these things where's not that clear, what the user is doing (I thought about proximity sensor as trigger for strokes in applications).
As a fallback solution for myself I was thinking about disabling all clicks in hildon home and writing some daemon to watch moves.
With my computer with phone, I can't send messages, so it'll have to wait, till I get to my computer without phone.
In the meanwhile, anyone else... ?