I didn't realize it was possible, but the Moviepro app is free today in supposedly allows 3K recording on the iPhone 5S.

https://itunes.apple.com/us/app/moviepro-video-recorder-pause/id547101144?mt=8

I need a 5S to do it seems.

Fun times. Filmic Pro has been my go to iPhone video recording app but with the announcement of iOS 8 allowing developers more access to the camera, it should be interesting what kinds of thing will be done with Mobilevideo.