The Garden Igloo Kit. in a few different versions. could be a greenhouse +/or alternative to tent accommodations to house a few more summer retreatants. not particularly cost effective though, in my humble view.
The Kodoma Zome as so it's called is a giant hanging hammock/bed/couch that you can hang from a tree branch or purchase an optional tripod to hang it from the ground, where you can relax outdoors whil.