Luke Redpath has also published an interesting post: Pushing events to your iPhone using WebSockets and Pusher
http://lukeredpath.co.uk/blog/pushing-events-to-your-iphone-...
Growl could probably do the same thing, but I already have notifo working and I'm a cheapskate. (Plus, IIRC if I want to use Prowl I need to have Growl running on a PC somewhere).