By showing people you trust that your battery's nearly empty, for instance, they won't be as worried in case they can't get in touch with you for the next hour or so. On the other hand, if they know your phone still has a lot of juice left and you're not picking up when you're supposed to be free to talk, then they can take action to make sure that you're safe. It's a small change with a big potential when it comes to safety. I can see myself taking advantage of it if I'm going to a place I'm unfamiliar with or any area I know could be dangerous. If you want to try it out yourself, simply fire up Google Maps, go to the app's menu, then to Location Sharing and choose who you want to send your location to.