The WiFi thermostats (Nest, Honeywell etc.) are typically designed for home use. Most homes use 24 volts AC power for the tstats. The RV has 12 volts DC power available, so that's hurdle one. Then, in the case of the Dometic tstat, some of the control logic occurs on a board under the air conditioner cover versus all in the tstat.
I researched this some time back and did come across a thread on another forum where a guy was able to interface a 24 volt AC tstat to his coach system. But I believe he had a simpler setup than today's more modern coaches.
This all said, I'm sure it's only a matter of time before Dometic or someone else comes out with one for the RV. I'd into home control and home automation and plan to bring some of that into my RV soon. So I too will be asking the same question you are - soon enough.