There's an app you only need to launch when you're not actively using your phone. This app will show you ads and your phone will make money. Completely passive.
Your credit can be paid out via Paypal, Amazon, Bitcoin, Ethereum,...
Just register at https://goo.gl/rryRfv and start the app.
Not sure how legitimate this is. If I had to guess, I'd say the app steals your info and gives you fake money. What would the balance even convert to? Funny idea, though.
I will share my experiences here. ;)