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.