If you don't have the fancy UI on the front, you're going to want a fancy UI on a web interface.

The niche market these products are selling to definitely want the nice UI. These things are going to get installed likely as part of a multi-thousand dollar home automation system. When someone's dumping that kind of coin they expect a certain level of polish.

I wouldn't tackle the task of competing unless I was sure I could architect something superior (which I'm confident I can) *AND* deliver it for a price where I could make decent money with decent volume. It's this execution bit where dreams meet hard reality and hard finances.

Thermostats aren't something I've seriously looked at, but I can see at least 1000 hours for a team of 3 to 5. I honestly think 200 hours is somewhat of a pipe dream for a marketable product. Which is both unfortunate, as I'd jump on it if it were, and fortunate, which means that not every other Tom Dick nor Harry will jump on it either.