Is it possible to view video stream (H.264 live feed) over RTP/RTSP in iPhone natively? If not, is it possible to write an application for this purpose?
Sure it is possible, in fact others have done it already, see e.g. IPVision from TTrix.
Seems that the Live555 libraries can be compiled for iOS. See this SO question:
Sure it is possible now. Previously, RTSP is not allowed in AppStore, though someone migrated VLC to iPhone, but that app is removed from AppStore, you can only install it via jailbreak. Now Apple doesn't insist this rule any more, so you can write RTSP player on iPhone as you will. In face, I've done this a few months ago, migrating ffmpeg & live555 to iOS and make an app, absolutely feasible!
来源：https://stackoverflow.com/questions/6691147/h-264-over-rtp-rtsp-iphone