Multiple TV's Multiple Sound

Hi,
I have 4 Tv's that are in 1 room. I am trying to find a solution whereby I can listen to the TV's by plugging a headphone into something that will allow me to change the channel (audio only) and obviously volume up or down BUT only on the individual unit where the headphone is plugged in.

I hope im explaining this correctly, you see a similar set up in many fitness centres where they have tv's on the wall and when a user uses a treadmill or bike they can plug their headphones into a little box that only has channel up and down, you cant change the actual tv channel but you change the channel you are listening to....is this a radio frequency set up? If anyone can direct me to the hardware that I require please help as I need this quite urgently.

Thanks in advance

thanks for that,

would you know any specific brand that I could look for that allows for multiple audio inputs and selection of fm frequency?