One approach is to use EMS to modify the setpoint temperature of the zone based on the wall temperature.

The actuator is:

EnergyManagementSystem:Actuator Available,ZONE NAME,Zone Temperature Control,Heating Setpoint,[C]

This would allow any equipment, not just IdealLoads to operate based on wall temperature.

Alternately you may want to look at the ZoneControl:Thermostat:OperativeTemperature object to see if this can do what you need without using EMS.