Been thinking about communications when towing my daughter in a trailer. I've read about parents simply using a baby monitor in the trailer while the kids can't talk. This two way radio came up in a Google search, appears to strap on to a bike helmet and is well rated on Amazon. Or you might like to ask for opinions on Reddit from the bike touring/tandem crowd.
We're all very different, with respect, that would be just as ridiculous, FOR ME. That said I would look to any of the systems commonly used by the PTW (motorcycle) world. ModernVespa.com had some good threads over the years. Unfortunately there aren't many great bike helmets setup for coms.