
Unstretched the hairbands are conveniently small, but they can stretch around the foot of my largest glasses. They do that job well.
Perhaps similar could be used for a walk-about port tasting with many people and only a few different ports. Each glass might have two hairbands, one to identify the port (black, grey, or white hairbands, not port), and one to identify the person (red, blue, green, yellow, etc, and many variations of stripe).
My instinct is that this is good technology in need of a purpose.