Being out of aluminum puts the price up too much. As much as I think it's an interesting idea, $20 for something that only serves to help me find my keys is a bit much.
Edit: I checked on Amazon and there are similar products for ~$10
<Moderated due to Amazon referral Link>
M455dr0pActually it's not really. If you drop a tritium pellet in these (amazingly simple to find) it glows on it's own. The keychain you linked is battery operated and thus need to be turned on, negating usefulness in find said keys. The glow in the dark pellet is fairly useless thou, unless your in the habit of leaving you keys in the sun all day.
With the self-luminous tritium thou, it's surprising how fast you look for the glow to find your keys. I've got this style and the isotope on my keys & EDC flashlight to simplify locating them.
Tritium has a half life of some 12 years, meaning still glowing at fourth capacity after 24 years. The fobs on this drop do not include tritium vials (that's a DIY mod) but recharge infinitely under light exposure. I imagine they're also slimmer than battery powered fobs.
Edit: I checked on Amazon and there are similar products for ~$10 <Moderated due to Amazon referral Link>