Ajax maybe to push new content – Help

I’m hoping someone can help with their knowledge of a plugin I can use OR maybe steer me in the right direction.

Ultimately I am trying allow admin to have the ability to be able to make a selection of an option on backend and upon the admin clicking save on the frontend of the site on a page WHILE any visitor is already on a page WITHOUT refresh (because admin just selected an option) this option (using ajax) (or some kind of polling) can no show on the page.

So, here is a simple real world example:
There is an option page on backend / admin, admin selects “apples”.
There are visitors already on the website home page, because admin selected “apples” an image of “apples” appears on header of the page without the visitor having to refresh page.

Now admin selects “oranges”, the apple image is now “oranges”.. visitors of home page now see “oranges” without page refresh.

As anyone aware of a plugin that could get this accomplished? If not, can someone please steer me in the right direction with any terms or links to info that I can google search for, I really don’t mind reading and learning.

Thanks is advanced.