iphones' notifications require more than just a device. if you look at apple's SDK, it has a bunch of infrastructure (apple's servers, and the ISV's servers) working together to push notifications to the phone.

and this makes sense because it's one of the best ways to solve the "always-connected-but-sucky-battery-life" problem.

so there's currently no way for the n900 to do this unless it remains always connected and polls facebook.

btw, isn't there an SMS interface for facebook?