I just picked up the new iPhone 5S, and found out that its camera can shoot in 120 FPS, bad ass!
I Imported the videos to my mac and edited them (lowered the speed of some sequences to 25% - 30 FPS) The raw video you get is actually 120 FPS, so you could play it in 100% with insanely high framerate if you don’t compress it.
If you edit the video on the phone, you get this smooth speed transition, something I didn’t get when I edited my video files in Screenflow. However, this may be possible in Mac OS 10.9, Mavericks? (I’m still on 10.8)