The Find My IPhone app works well, but you have to have good cell coverage for it to work. You also have to have active cell phone service, so using it with an "old phone" isn't really an option, unless you somehow have wifi in your recovery area (in which case you probably wouldn't need a tracker).
There is a Garmin Astro, I believe, that can be tracked by a web GPS app, which would work about the same as a phone.
NAR, TRA L2
Member: CMASS, MMMSC
"I haven't slept for a week because that would be too long." -Mitch Hedberg