We have a Garmin set up for our coon hounds, but it sure wasn't cheap!
I think there's going to be an absolute revolution in this market in the next year or two that will knock the bottom out of Garmin's market, working on one myself with my brother-in-law.
Look for "child trackers", or even a cell phone app that tracks cell phone sim cards, then buy a crappy tracphone or used phone that's still active.