It isn't exactly "live tracking," but PackJournal (intended for keeping a blog while bike touring/backpacking) does a decent job of updating with your most recent location. Your photos and journals show up on a map, even if you were offline while writing or snapping photos, and your home page will display the most recent location from which you logged in or wrote a journal entry. So if your family sees you haven't moved in the last few days, they know something might be amiss. And you can customize the privacy of everything.

The app is free, the website is free, and maybe you were thinking of keeping a blog anyway. And since you can also add a fundraiser to your page and even keep a small amount of donations for yourself, you can essentially get paid to use it.