Heating & Cooling / Thermostat question

[IA_Chiefs_fan]

I have a pretty large house and all five bedrooms are upstairs. The problem is the downstairs is always several degrees cooler year-round and I like it to be cool when I sleep. What I'm wondering is if they would happen to make a dual thermostat system. It would be great if at a specific preset time the thermostat upstairs took over from the one downstairs or vice-versa. The second thermostat would need to be wireless too. I do not wish to spend more than $100 to remedy this. Any possibilities here???