I'd like to know if a Nest Thermostat would be allowed by halacha? They say it programs itself and it realizes when you come home, so when you come home on shabbat, the machine will detect it, and it will adjust itself accordingly.
I don't own this machine, but maybe there would be an option for it to only work on a schedule on certain days, which would solve this issue totally. But let's say there's no option; what would be the halacha?