Las Vegas, Jan. 12 -- Many of the hottest new gadgets are also the nosiest ones.

This week's CES tech show in Las Vegas was a showcase for cameras that livestream the living room, bathroom mirrors that offer beauty tips and gizmos that track the heartbeats of unborn children. All will collect some kind of data about their users, whether photos or monitor readings; how well they'll protect it and what exactly they plan do with it are the important and often unanswered questions.

These features can be useful - or at least fun - but they all open the door for companies and their workers to peek into your private life. Just this week, The Intercept reported that Ring, a security-camera company owned by Amazon, gave a variety of employees an...