I believe there is rapid fire mode for the camera on the newest iPhones (possibly only the 6+), but that isn't over a long time, just simply 1 per second as long as you hold the button.
I actually googled it. It is called 'Burst Mode' and is available on the 5s (and beyond I suppose). You don't even need to activate it, simply hold down the camera button and it will continue taking photos once per second until you let go.
edit: Just did this on my iPhone 6, and it is way faster than 1 per second. In a second, I took like 12 photos. Probably not what you're looking for.