Electroneum released mobile mining App on Android and Apple. That's looks pretty cool. Have you tried that and what do you think about that?
You can dig a hole with a spoon. But it will be slow and inefficient. Why would you do that? There is a special equipment for coin mining. In this way you will destroy your smartphone and will not earn coins. The cost of modern smartphones is comparable to the cost of GPU. I don't understand why this is necessary.