It has since been taken off the Google Play Store in accordance with their updated policies, but I used to use an app called Crypto Miner by Jesus Oliver. That's legit -- actually mines... albeit very, VERY slowly, as everyone else in the thread has already noted.
It's highly unlikely that your mobile phone will hit a share that gets accepted by any mining pool, in other words, that app you mentioned or any other app for that matter does not really mine bitcoin, the most common thing they do is collect your data and sell it for marketing purposes, they get paid for it and pay you a small portion, there could be a few more ways they can make money of your phone resources, mining bitcoin isn't one of them, so just because an app pays you something (large or small) it does mean it actually mines bitcoin, it's most certainly doing something else that generates some sort of a revenue someway, somehow.