> I'd much prefer to see two separate decorators here. 

No problem. Now to name them...

> We might even drop the call option altogether: did you have specific use-cases in mind for this?

I had `traits.trait_notifiers.ui_dispatch` in mind for `call`. I would be happy to drop it if we had a `UIExecutor` that dispatched to a UI thread. (That can get pretty hairy, though.)