I dont know about destroy but the power consumption would be far too much to justify.    Also heat, alot of these phones cannot handle the heat they producing if used 100% every hour.     However its not impossible in some alternative way like proof of stake would be possible.

Its not encouraged to do so for staking because to carry around your asset worth on a phone would be fool hardy and make that person a target.    The POW reason is that mobile phones are just not that efficient vs normal circuits which can be cooled and stressed to a greater limit.

The biggest thing about a mobile phone always is its unplugged mobility and communication and I agree that is a great asset that could be used in a network.  Its most commonly used in social networks only informally but I dont think its impossible to have some security improvement occur from distributed mobile users