You can do this with Find My iPhone too. The issue in question, though, makes both of those useless as you'd need to unlock the phone, open the app, navigate to

You can do this with Find My iPhone too. The issue in question, though, makes both of those useless as you'd need to unlock the phone, open the app, navigate to the device in question, and then lock it. If you're in the presence of an attacker or other intruding force, it's doubtful they would let you continue use of your phone in that manner. Tapping the power button can be done subtly and quickly enough to still make it useful.