I'd definitely like to second the question about more adapters being made... I really want that GB one. And in case it matters I'll buy an NES adapter the instant it comes out, if one is in the works.
Looks like there's SMS adapters available on dragonbox at the moment. Not sure if that's new or they just never ran out.
EDIT: Oh okay, just looked into that twitter post and I see they say more GB adapters will indeed be coming. Yay!