Thanks for all the lovely notes! Basically its just a folded over tube of fabric, that should fit your hips if you want to wear it low, and a slightly larger tube for the skirt. The only really hard part was easing in the knit so it didn't bunch too much.
I just got a new sewing machine and made my first project. It's a skirt that converts into a tube dress. I based in on my favorite summer H&M skirt. The top of the skirt folds up into a tube dress. My lovely brother Matt helped me take these pictures.
PS I can't figure out why that one pic is ginormous.
Thanks for all the inspiration everyone! Keep it up!