It's a lot of fun to play "fake Weissenborn" with your acoustic, especially for this price. Get yourself a tonebar and thumbpick, tune to something easy like open D or open Dsus4 (DADGAD) and off you go!
Pros:
Cheap, easy to use (just loosen your strings a lot, slide the nut under the strings over the actual guitar nut, tighten strings back)
Cons:
Well... It doesn't look very good... But for this price and purpose, who cares, really.