Your friend is correct the on the slow moving props. I have seen the indoor plane like in the video flown at a hobby show in Pasadena,ca. back awhile ago. They are like butterflies floating around for long time around the convention center.
The indoor micro r/c stick type prop planes are really neat also to watch. The indoor micro R/C guys were the one that pushed the envelope in micro R/C equipment to weigh a couple grams or less.
The materials they use are balsa wood and carbon fiber with a ultra light weight mylar type film for wing and prop coverings. I use to buy the film from a guy who sold it to cover my Epp foam wings and tail feathers on my r/c hand launch glider that I designed that weighed in at 5.5oz called The Cetan.
Here's a link to freeflight.org if you want to start play around with micro flight
Plantraco offer ready made planes and the best radios for micro indoor R/C gear,Plus they make micro blimps that I have owned that are pretty cool.