So you want a freestanding shelter that isn't a tent... Pretty much, if it's freestanding it will use poles, and if it uses poles it'll go up and look pretty much like a tent. I realize this doesn't help you choose such a shelter, but I'm not aware of anything existing that fits your bill. Closest option would be a hooped bivy sack, maybe a Bibler tripod bivy. Pretty hot in summer, but you could just sleep on top of/without bag, maybe. Cheers-
Edit: Integral Designs makes several nice bivies, too. In eVent, even.