According to this Reddit Experiment
https://www.reddit.com/r/Electroneum/comments/7j73su/mobile_miner_hashrate_experiment/Even the Snapdragon 835, which can be considered a high end mobile CPU only managed to get 20h/s
That is really slow, there's no way you could profit from it, not even mining Altcoins like Monero or Ethereum.
Forget about creating mining app, unless phone manufacturer decided to make phone solely for Mining

It isn't viable to mine from Android but it's quite a nice app nonetheless.
Also, there might be a way to connect a USB asic to a rooted tablet to get it to mine but it'll probably overheat or damage RAM due to the intense process needed.
I actually once tried to mine through phone, it got so hot that my phone overheats and shut itself off, the battery got bloated due to heat and I had to replace it.
Not a fun experience nonetheless.
For the record, taking the back off, pulling out the battery and mining with some sort if liquid cooler could possibly stop the phone decaying so much. It'll absolutely still die of overheating, but you might get a little more time before it does (fans won't do anything as everything's encapsulated too tightly). Though it's actually not the worst thing that could've happened, if not done properly and the battery overheats too far, they can combust and cause a much greater issue.
The OS is pretty light on all of them and it's expected by the manufacturer that they won't need as much control of resources for what you'd generally use a smartphone for (the most intensive thing probably being streaming a movie or video calling normally).
it could be a device that we use explode ,, it might be the worst possible thing that can happen ,, and actually I was less understanding about this mining app ,, but what I know we need something to make in cooling