This APP might be able to do what you want. It
This Advanced Thermostat APP might be able to do what you want. It is actually designed to use an on off switch controlling heat but it likely can work with a thermostat as well.
Having said that you must consider the reaction time of the sensors and how often they report temperature. A battery operated device that only reports every 10 - 15 minutes will not be able to control the temperature very well.
