Really Nice Idea!! I think the only reason I know how it done is because I'm an apple fanboy so I know a lot of ideas used with iphones and I have a suspicion that I know how it's done. BUT IT'S FANTASTIC!
I'm pretty sure I know how it is done because you flashed a bit. Also, another problem is that when the screenshot supposedly was taken, it looked like the 4 of diamonds, so a spectator might be suspicious because they saw it stop on a red card, but the screenshot was a black card.
I like it because it's straight forward. Good stuff!
It's not fishy like a number of smart phone "magic tricks" seem to be.
Of course, I'd rather do the classic effect with an actual deck of cards, but having this ready on a phone is smart since with me even at work my phone is glued to me whereas if I'm not at my desk then I'm not at my deck. ;-)
Note that your technique (under my assumption of what your technique is) is not iPhone-exclusive.
In the default "Gallery" app on Droids, you can play a video and when it finishes it holds on the last frame. You can then swipe over to the next/previous image/video file just as cleanly.
With Android v4.0 and later, you can take a screenshot by holding the Power button and the Volume Down button.
Just some useful information in case you have ambition to make a video for release on The Wire or such -- just grab a friend with a modern Droid phone and show it with that as well. =)
Looks pretty sweet. Never seen a trick like it. One suggestion is that if the card is forced, stick a 7 of clubs on the back. Or like a pictured case or something. That way, instead of the mind-reading, you can have a sweet reveal. I don't know, just a thought. Looks awesome though
I like it, it's a really cool modern version of the riffle force. Lots of applications, I agree with coinartist I think it would be cool to have it like stuck on the back of the phone... maybe inside the phone case? Unfortunately my windows phone doesn't have a screenshot feature so I can't use this trick but best of luck to those that do