I can't say how this should work - that's up to you to work out. One solution might entail everyone synchronizing their smart phones. Another solution might involve a receiver and a room full of bluetooth headsets.
Perhaps I am thinking too narrowly about the problem, and some brand new mode of teleconferencing will render speakerphones obsolete. Regardless, thanks for your consideration! I look forward to never having to talk to a speakerphone again.