Strange coincidence! A friend on fb posted a message tonight along the lines of "going to a new friend's house, if I don't check in by midnight, call the police

Strange coincidence! A friend on fb posted a message tonight along the lines of "going to a new friend's house, if I don't check in by midnight, call the police". I've definitely let a friend know when making a craigslist or airbnb transaction. I probably would rather just let a friend know where I was going but it's nice there's an alternative and I'm sure this service can be run rather cheaply.