Uniquely Identify people in a room

I would like to start a project that basically will identify people as they enter a specific room. I do not want to use a proximity reader. In a perfect world that will happen automatically.

Ideal situation is someone enter a room and then I can detect that with the photon and raise an event.

My question is. Can I accomplish that with RFID ? I have done some research and for most cases RFID only works if you have a reader and then use a card or a key fob but it does not support big distances and if you have the fob in your jacket is even worst.

Does anyone know any other sensor that I can use ?