Magic playing cards(Gyroscope)

Call the spectators around you, shake your smartphone to shuffle the playing cards (every "shake" changes the position of 8 casual cards) , ask to choose a card, incline the smartphone to your spectators around you (2 or 3 signals by the gyroscope) and then ask to touch the display to stop the playing cards on a specific card, the chosen card!
ONLY FOR MAGICIANS! NEED TO PRACTISE BEFORE TO USE!