Porting yenten minerd over to Android should be quite easy. Here's the original bitcoin minerd ported over: https://github.com/0xD34D/android_external_cpuminer I'm no dev though, so if I would try this it'd take a while. Imagine all the old or broken phones that could be put to good use.
I would pay a bounty for that. And also a mobile wallet.
True. I'm trying to figure out the best way forward for hash/watt then invest in of a bunch of them. Also I am designing a cryogenic case (immersion in liquid nitrogen) so I need to have picked out the best board to use first.
When I do I will open source the case design and also sell the cases. I was thinking mini-itx with intel atom but if android is this good and also lower power I will go that route and mabye put 3 odroids per case.