This is a great App for your iPhone it runs in real time, very useful if you are filming several locations in one day, type the persons name 
in the “dir” column and you have a record of the interviewee , date and time it was shot. This I might add is more useful for the editor who in many occasions is not with you on the shoot.
Along the top you will find ROLL in my case this would correspond to what SxS or MxM card I was using, then you have SCENE which can be changed and lastly you have TAKE which changes every time you activate the clapper. You can change the FPS from 25 to 50 if you are filming 720 50P and you can also change the camera number.
I love the concept and it works to a degree but it can be fiddly to activate the editing screen but for £1.79 it’s a snip for such and advanced pocket clapperboard.
I assume that you could use this on an iTouch too – not just on the iPhone – but how much does it cost to download from the iStore?
£1.79 from the photographic section in Apple iStore Apps. It also works on the iTouch.