AppKarma is a reward app that lets you earn rewards by playing with games.
Earn free gift cards for trying new apps. Redeem your rewards for Amazon, iTunes, Google Play, and more.
Download from play store and App Store.
I believe there are some apps that are free and some are not but earning off it can be one of the most interesting things that can ever happen to anyone, especially leisure apps or maybe get fit apps...that will be a good motivation isn't it?