The question isn't entirely clear, or at least to me its not! Are you looking to ensure the temperature doesn't fall below a certain point? (e.g. worried pipes freezing, so you would like to ensure home temp never falls below say 40-45 degrees). Or are you worried about guest changing the AC to too cold a temperature, say 55 degrees, running up your electric bill?
With either case I would recommend Ecobee thermostat. You can set a low temperature threshold ensuring temperature does not fall below that limit. Also you can set a minimum temperature AC can be set to, for example 70 degrees, to ensure they cannot drive up your electric bill. Once either of these settings are set-up you can then lockout the thermostat with a password to ensure guest do not change the parameters you established. Pretty sure Nest Thermostats have similar features (I used to have one a few years ago but forget at this point).