I don’t know much about this, but it looks like it might have potential. Not much details about it but it looks like you can collect assignments through email and mark them up immediately and then return it to students through email. It might be worth checking out. I’ll definitely let you guys know if it’s any good as soon as it comes out.
You enter your email here and the developers will give you early access.
Steve
teachingwithipad.org 
Hello there! I could have sworn I’ve been to this site before but after checking through some of the post I realized it’s new to me.
Anyways, I’m definitely delighted I found it and I’ll be book-marking and checking back often!