I just ordered a couple. I plan on gluing a piece to a key blank, and then putting a piece of shrink wrap over it. Then I can put it on my keychain.

Now that I think about it, perhaps gluing it to a spare house key would be a better idea, a key blank is rather useless. Then if my main house key fails for any reason, I can pop the spark rod off, scrape the glue off, and then get in the house.