What a great video! I've seen a number of different 1 or 2 string instruments in my travels, but never one played like that.
In a Sussex recording studio, the owner had a Japanese instrument with a kind of round bowl and (IIRC) just one rather slack gut string and a fretless neck. You plucked it while sliding and pulling off on the neck and got very Japanese twanging sounds out of it.
I also have memories of when I was at school and a teacher demonstrated a strange single-stringed bowed instrument that had no body, but a neck with two pads that you head between your knees (seated) to play... and a brass horn!
I love these quirky, unusual instruments and it's great to actually see them played.
PS: I've also got a 4-string mandolin that I bought in Nepal (I think). Nice to look at, but impossible to keep in tune and pretty much unplayable!