I can't figure out how this could be done wirelessly (but I am not in the conference industry). The issue is about one source and 20 monitors. At my work I have a setup where a computer in my office is able to stream wirelessly to an TV with an AppleTV, but the watcher chooses the video since the AppleTV, like a Roku, Slingbox, PS3 and other DLNA devices, are media servers that provide what is requested at the viewing end. I can't see how the videos could all be in sync since the media is selected at the viewing end (pulled).
Maybe there is a device to hook up to a monitor that can receive signal wirelessly when video is pushed to it (like a projector receiving from a laptop), and then you would hook up all the monitors to their own device. Pushing the video would then go to all the monitors connected to the computer. We use Apple TVs like this too, but we can only push to a single device at a time wirelessly.
If you find a solution, please share. I would be curious.