First time posting. I have a very old home with no C-wire solution at the moment for smart thermostat. The only option I have is the LUX GEO. It's plain, maybe cheaply made (many reviews complain of cheap plastic), but it will work with my 2-wire oil radiator furnace. Can use c-wire, or 2 AA LiIon battery. It's the cheapest I found. Most places are over $100. Excited to try it out. Hope someone else can benefit from this deal.