I Told You So
Call the match before it happens. Beat your friends. Keep the proof.
Start a League for the competitions you follow and invite your friends with a QR code or a link. Every round, pick the result of each fixture before kickoff. Your pick is sealed until the match starts, and a correct call scores more the less likely it looked.
A pick costs nothing. Points are a score: they cannot be bought, sold, transferred, or exchanged for money or prizes.
Where to get it
ITYS is in an invited beta on iPhone. It comes to the App Store once the beta is done.