Download this free iPhone app named Who's Online :
Who's Online Lite for iPhone 3GS, iPhone 4, iPhone 4S, iPod touch (3rd generation), iPod touch (4th generation) and iPad on the iTunes App Store
You can see who is online without being online yourself!
Get notified when your selected friends become online..
Get notified when your selected friends checkin in near..
Works great and there is a free version
