I discovered today that the Moto X has a "Trusted Devices" section - functionality I'll let Geek.com describe, as they certainly do a better job than I could:
The concept is fairly simple, but works so well that it is easy to forget it even exists. After you pair a Bluetooth device you can go into the security settings on the Moto X and flag it as a trusted device. Any time your phone is close enough to connect to this accessory it’ll recognize it as a trusted device and remove any security you have set up on your phone (since it assumes you’re present). If you use a password, pin, pattern, or face unlock to get into your Moto X under normal circumstances, those security measures will be temporarily removed whenever your trusted Bluetooth device is within range. This means you can walk away from your phone and know that it is locked, but when you go to pick up the device there’s less work required to get inside because it knows you are (most likely) the one picking it up.
I actually use a similar third-party app with my Pebble called Pebble Locker, and I have to admit, it's certainly handy.
At the risk of continuing to fuel the "Is Google making a smartwatch?" speculation - could this be helping lay the foundation to a Google-made smartwatch? Perhaps it's nothing more baseless speculation, but it seems as though the Moto X is designed around "convenience features" that will sell well, both on the floor of a carrier store or through TV ads, and I think this kind of thing could fit right in with Active Display, Touchless Controls, and Motorola Assist.
It's hard to convince someone they need to buy a Pebble because "oh you can download a third party app that enables your device lock if you get disconnected it's really cool TRUST ME" - but I think it's a far easier argument to make if that functionality is built directly into the phone already.
It wouldn't necessarily just be the "Trusted Devices" functionality, either - I can envision Touchless Controls working with a smartwatch, too You say "Okay, Google Now", and Google Now comes up on your watch, rather than your phone, which might be across the room, in a pocket, or otherwise unavailable. Or, the opposite - you press a button on your watch, and Google Now is ready to listen on your phone or watch.
Maybe it's not a mainstream enough use case to make it into TV ads either way, but it seems like it's certainly worth considering - and it's not like Motorola doesn't have a history of smartwatch-like devices.