Replying to Rail ipod app?

I was just wondering if this already existed, an app for ipod or iphone that is kinda like a trick selector... so you like dont always to the same tricks on rails and it makes you get better and practice ones you dont do really often. so you shake the ipod or iphone and a random trick appears.. say 270 on switch up bs 270 out?? so i was just curious, cause its preseason at my hill and we got 2 rails and we climb back up , just so we dont always do they same trick, and so it also makes something really fun funne rbecause it kinda gives you a challenge.