technoskins - eyeglass retainers

Anybody used technoskin eyeglass retainers?

I stumbled upon these while looking at 4-season tents discussed in another post. These retainers both cover (like a hammocker's snakeskins) and clean your glasses.

My fear is somehow losing my eyeglasses on a hike and groping my way home. Are you using anything better?

I tried either this product or something very similar a couple of years ago. Didn't work very well. I always carry an old pair, sturdily packaged.