Simplest one that exists is GetGems Messenger, you just share your unique url through the app (supports bitcoin) which is automatically attached to your username and if someone downloads the app you get rewarded. You can share this url with your social network like WhatsApp, Facebook, Twitter, Viber, Telegram, Instagram, Snapchat etc. You can also put your unique url in your signature or any other site. 3 referrals gave me 75 Gems which is 4000 bits and i didn't have to do much really so if you would have a large social network it would be pretty nice, soon there will be more reward models implemented besides referrals.
Once you click on referrals you can see which of your friends downloaded the app, the world first messenger app doing it in such easy way ladies and gentlemen, there is quack messenger with fiat but it's a fail you have to wait 30 to 90 days before you can cash out. Power of Crypto.
