The beats having to type your password over and over again as you run to grab water, a printout, talk with someone, etc. The downside is if you leave you phone at your computer or someone steals your phone they can pretty easily get in.
That being said it translates real well with the concept of ID cards that you scan to get in a building. People can always steal those too.
I am pretty sure that apple and google are already integrating this into their respective products as we speak.
To get it simply, "sudo yum install blueproximity"

Ironically I usually use that when I'm at Chipotle!
I have seen this at Guercio's.
that does look like it would be tasty