The mobile mining for Electroneum isn't really using your phone's hardware to run proof of work using cryptonight. It's just the mining "experience" as stated in this blog post.

The mobile miner is completely revolutionary way to earn cryptocurrency by “mining” on your phone. In fact your phone isn’t really doing the hard work of mining the coins, that’s already done – this is a mining experience. “What’s that?!”, I hear you say, well, our mining experience looks like a miner, feels like a miner and pays out real Electroneum cryptocurrency, just like a complex command line miner running on a linux computer – BUT all you need to do is click the “START MINING” button on a free app to earn cryptocurrency! These coins are nothing to do with the coins emitted by the blockchain as part of the blockchain reward. Blockchain miners are still vitally important to Electroneum, but full mining is too complex for the average user. The mobile miner is a separate algorithm that rewards users with ETN cryptocurrency at no cost.