Maybe the big phone manufacturers could start putting ASIC chips in the phones they sell and profit that way. Just one chip per phone, and it would be a small chip so the phone doesn't get too hot. It would stay dormant in normal use and would only be activated during times when the phone is fully charged but still connected to a charger. That way, the customer doesn't notice.
This is actually bloody genius.
About, oh, I dunno, 50% (At least) of the world's population has a Android or Apple device, and if companies started adding ASICs like what you said, that would allow companies to earn about 250 BTC, if they have all 3,500,000,000 mining all the time. Realistic estimates would put it at about 100 BTC, at best. Not everyone has it hooked up all the time.
So companies could be mining pretty big amounts, the question would be if the companies would hold it and wait, or sell it off...