I'm thinking about a device that can communicate with a phone. Think of it as simply something that will tell an app "1" if it communicates with it, otherwise the app will remain "0."
But what I want is for it to, for example, be able to be placed on a table, and it facing a certain way. If two people are sitting opposite each other on the table and the device is pointing towards one of them, it will tell the person it is pointing towards "1" but the other person, who is "outside of the cone" would not get a "1" because of that and his app would stay at "0." The person it is facing towards could move to the side a few feet and no longer receive a "1" because he moved out of the "cone."
I know there are directional antennae, but that seems to be more about increasing the signal strength.
Specifically it would only need to cover a few square feet.
I guess bluetooth is really the way you would communicate with an iphone/android. Is this possible to work with bluetooth?