同时播放和保存视频?

I'm writing an app, part of which allows the user stream/play videos. I want to restrict the functionality so that they can only stream videos if they have a WiFi connection. I will then save the video so that when they have a 3G only (or lesser) connection they can't stream videos and can only replay videos that are saved on the phone.I'm writing an app, part of which allows the us