New iPhone IM app with Push Notification! http://digital.venturebeat.com/2009/07/08/ebuddy-for-iphone-joins-the-push-notification-bandwagon/
That means people can still IM you when you put your phone down or use it for something else like email or iPod stuff. Unfortunately, it only stays signed in for half-an-hour after you close the app, whereas the AIM app keeps you signed in for a whole day. There are several other shortcomings as well, which I won’t go into at the moment. I am definitely looking forward to the push notifications upgrade to Yahoo! Messenger.