Smart phones cannot be used for mining for Bitcoin or for any coins I think because the mining capacity and the electricity consumption for it is very large and smart phone cannot withstand at least 1% of its need. There are huge rigs and capacitors involved for mining now a days and smart phone will burn if anything tried now.
Mining altcoins like monero or electronium wont do any good because these are not too much in demand so one way or the other, mining using smartphones is useless. Besides, this is a very expensive method of making money. Mining demands a lot of requirements. Besides, smartphones have hardware which will wear out too quickly if used for mining.