I've seen something similar to that before.
I remember seeing an interview with Nuno Bettencourt who was doing some new Extreme recording at home. He had a box with a mic inside, foam on the sides and back, and room for the mic mounted in an shock mount. He was using it for isolation when doing vocal work at home. It was just a simple homemade wooden box, probably a 1ft cube or so. There was no front door. I thought it was an interesting idea.