These two items came across my river at the same time.
Highlight is the current frictionless sharing leader. It's constantly broadcasting your location back ot the mother ship, without you having to do anything to make it happen. No check-ins as with the Foursquare generation of sharing apps. And Highlight is connected to Facebook, so it seems likely you're sharing at least some of that with Facebook as well.
There's a big test in the law around privacy. Did you have a reasonable expectation of privacy? Then if the government wants to invade your space they need to get a warrant. However if you didn't have a reasonable expectation of privacy, they can go ahead and watch you. Without you knowing.
This is a big deal these days. The government doesn't necessarily believe you have a reasonable expectation of privacy in your email inbox and outbox. Therefore they think they should be able to have a look, whenever they want, without a court order. The companies that provide email service, at least some of them, disagree, for now at least.