We use a Cobra two way radio for baby monitor (which essentially turns it into one way radio). VOX works OK from inside the trailer but it's quite sensitive. I doubt it would work well with wind noise, traffic etc. Motorcyclists seem to use same radios with the optional "handsfree" set (earbud plus microphone) but they tend to have full face helmets, a lot less ambient noise there. Maybe just use the earbud/microphone with the manual "talk" trigger?

--J