I have to agree with Nick about the heating, in all the time I used the remote system there was only one failure and that was to switch on so we arrived to a cold boat. I didn't check that I had got a reply from the system to say the relay was on so the SMS must have got lost on its way to the boat.
Never used the diesel heater as frost prevention preferring to use electric radiators, worst that could happen if they stayed on was the meter running out of credit and that I couldn't top up remotely 😲