Any culture that had bows and arrows soon learned to use their bows to make music, so the mouthbow has been around since the beginnings of human history.... 20 thousand or 200 thousand years?
My mouthbow playing is based on the Appalachian mouthbow as I learned it from recordings by Buffy Sainte Marie. In the southeast United States the mouthbow probably originates both from the Native American culture and from west Africa.
Groundhog is a children's "play party" song I learned from Buffy Sainte Marie's recordings ... a mostly one chord song built on bugle call notes. The open string makes these notes easily so this is a good place to start learning how to play.
This is a diagram of my mouthbow design, but all you need is a piece of fishing line and a stick.... (any string, kite string, even dental floss works). You don't have to wrap around the end of the stick, but it's easy to do. I like 30 or 40 pound test nylon monofillament and you can get it for free at fishing supply stores that put new line on reels.
If you want to make one with a tuner, you can use a peg in hole, a brass bolt with a groove sawed into the end facing up, or get a used tuning machine from a guitar repair shop... they replace the whole set for one bad tuner and the other five go in a box or a drawer. The repair shop also has old frets and can cut you a piece of fret wire too if need be.
(Download making and playing directions here: Making_and_Playing_the_Mouthbow.doc
Buffy Sainte Marie holds the mouthbow across her mouth, but I hold mine in front. I think this works best for recording, and playing with a mic but I'm not sure it makes any difference. I think the player hears it better the way Buffy plays, because the sound is reflecting off the bow and into the ear.