Security vulnerabilities aside, I just don't see people gravitating towards this.
Pick up phone, hold it out at arm's length in front of you. Hold it real still. Now wait. Bloop bleep boop now it's unlocked!
Compare with:
Pick up phone, swipe your unlock gesture. Hurray!
For something the user is doing constantly, many times, every single... I just don't see why anyone would pick the more uselessly time-consuming (and more effort required) option.
I think it could be useful if the camera has a zero shutter lag as it is in the nexus. A scenario coming to my mind is maybe hands-free interaction with voice commands while driving. Anyway, it don't think locking a phone has a security connotation here, but it is a way to avoid any accidental launch of application/typing.
Lock the phone and carefully look at the screen from a few different angles. Chances are that you can clearly make out the greasy trail of the unlock pattern. I switched back to a PIN code when I noticed this.
Pick up phone, hold it out at arm's length in front of you. Hold it real still. Now wait. Bloop bleep boop now it's unlocked!
Compare with:
Pick up phone, swipe your unlock gesture. Hurray!
For something the user is doing constantly, many times, every single... I just don't see why anyone would pick the more uselessly time-consuming (and more effort required) option.