You can tell that I'm becoming a bit of a Facebook addict... but was thinking today it would be neat to have a mobile notification of new wall posts and inbox messages. I know you can probably get these if you are in the US and sign up for SMS alerts, but what about the rest of the world? How about someone builds an IMAP interface into the FB repository that implements the IMAP Push specification. This way the service itself can poll for new messages (maybe even having the notifications triggered via the SMTP alerts) and then expose the data stream via the IMAP interface. Then by establishing a new IMAP account on my phone I can then get immediate notification of the event - along with a link to the appropriate page on m.facebook.com.
Yeah yeah, there are probably a thousand ways to implement this, but this way at least you avoid having to deal with any SMS gateways. Plus I like mentally designing convoluted Wallace & Grommit-style systems (you know, where the candle burns the string that releases the ball that rolls down the ramp that fires a gun that shoots an oven on-switch that cooks some bacon and eggs...)