We could have the first Mining Dapps for phones, from the bloke that owns the company that has lead the field of research in this area. Think of the take-up in the underdeveloped world. Its a good job Charles comes for free, we could never afford this development milestone otherwise. He gets to test his Theories with a live network.
Think of the demand for 64GB and 128GB phone memory cards!
For phone? I think it is not good for the phone, because it will be very hot, lol, like PC. And power of battery is much lower than PC, have to keep charging.
Maybe just mine when you charge your phone so to help pay the electricity for charging. A smart contract could settle the bill with whoever you got the charge-up from. Maybe shops, cafe, Library, Post office or any public building in developing countries could offer charging. Moreover, a network of desktop harddrive mining rigs would supply the phones with an immutable decentralised cloud space for storage and dapps. If you already mine ETC with GPU, just add HHDs and software and your HHD mining and earning ETC.