Most iOS app that shows video are using it behind the scenes. It's even mandatory if you want to work over 3G: "If your app delivers video over cellular networ

Most iOS app that shows video are using it behind the scenes. It's even mandatory if you want to work over 3G: "If your app delivers video over cellular networks, and the video exceeds either 10 minutes duration or 5 MB of data in a five minute period, you are required to use HTTP Live Streaming. (Progressive download may be used for smaller clips.)"