http://mobile.foobar2000.com/
I'd kickstart them getting a half decent default interface for their main software. ;)
I very much like foobar2000, and I would likely use the mobile app. However, they seem to have a weird pricing scheme, those headphones do not appeal to me, and the other rewards are a no go - I do not want to have to pay for a broken piece of software; I'll beta test for free... but not if I have to pay.
I'd back it, but I don't use my phone/android system for music anymore since I got myself a dedicated music player.