FLASH BEAM by Martin Schwartz
A borrowed iPhone flashes magically to reveal a freely selected card as cards are passed under the iPhone flash light. No sleight of hand, no blue tube, no apps - the iPhone light is totally under your control to turn on and off. No reset -- can be repeated immediately. Use any deck of cards -- everything is examinable. You will freak them out when the light goes on and off with your magical gesture. iPhone magic is hot. This effect will blow your audience out of the box.