Today the POW of altercoins is base mailnly on:
CPU performance (few coin)
GPU memory speed (most)
Mining is also a 24x24x7 continuos work
It is impossible to compete with a Pc cpu or a GPU for a smartphone at hardware level.
The power ratio is 1/10 for cpu and worst for Gpu
Some one shold invent a new POW that equilize this hardware difference.
For example using a sensor related to mobile device...
You may gain coin during gym or run ... a more green coin.