Want to Scare your Friends, then this isthebest app available on App Store.
App has awesome feature which detects the app and scareyourfriends.
Very simple to use,

1. Choose app and/or Time
2. Select image and Sound

Ask your friend to open the app which you have choosed, onceyourfriend opens app, it will scare them
Njoy with this app and Scare your friends
Keep Scarring