Google on December 5 announced Trusted Contacts, an Android app designed to keep tabs on your location and share it with contacts of your choosing during an emergency. According to Google, an iOS version of the app is "coming soon."
After you add trusted contacts to the app, those people can view if you've moved around recently and if your phone is online. Additionally, your trusted contacts can request access to your location. You can then approve or deny the request, however if you're unable to respond within five minutes, the app will automatically approve the request and share your location.
If you're in an area where there's no service or your phone has died, Trusted Contacts will send your last known location to those requesting it.
That might sound creepy, but in situations such as a car accident where you could be injured and unable to use a phone, knowing your family has a way to find you provides peace of mind.
Conversely, if you find yourself in a dangerous situation or an emergency and want a contact to know your location and where you're going, you can share that information on demand. When the situation is over, you can stop sharing your location.