Recording slow motion video is something which is usually done by expensive professional cameras. However if you have an iPhone 4S, you're in luck.
SloPro a new app just launched in the app store that lets you record in slow motion, kind of. It's not true slow motion, but it's the next best.
The app recordes video in 60fps, double the usual rate of 30fps, then lets you edit the video to determine where you want to make it go in slow motion. And yes it does output in full HD 1080p. If you're an original iPhone user, you're out of luck unfortunately because the iPhone 4S is the only one to record in 60fps.
I used the app myself and was quite surprised to see that it actually works pretty well, giving a nice and smooth slow mo effect. It's a great way to show off stunts and tricks or make a mockery of someone because the audio is in slow mo as well.
It's free to download but to use the actual slow mo effect you have to buy it through the app, so it's actually £1.49.