First let's read what our illustrious Dave Jones have to say about a hardware project
http://www.eevblog.com/2014/05/28/the-economics-of-selling-your-hardware-project/
Considering how many options there are I don't think there is a very expensive project.
Second, let's go buy a programmable thermostat off the shelf.
Sorry, I just find the idea of building expensive hardware around an expensive, underperforming, overhyped piece of hardware utterly offensive.