I'm a heating installer. You are a DIYer, you have one at home.
I and my staff fit this stuff for a living, day in, day out. Hometronic can have an internet interface, this has been the case for some years. There is very little demand for that particular piece of functionality.
Besides me being a "DIYer", my day job for many years has been professional R&D in technology products, including interface design.. during which time we have conducted usability studies with 1,000's of consumers and sold millions of products!
Generally speaking, most people who would get excited about controlling their heating from an app, or via bluetooth from a device, also want control of the other house functions. This is a niche market currently addressed by a number of small fry systems integrators.
The heating industry appears to be stuck in it's ways, reading posts on this forum shows that many RGI's are resistant to change. If the RGI's don't 'sell' the concept to consumers, there won't be the demand (initially)... our studies have shown many customers like to 'see' new technology, it's only then they realise they actually like/want it.
However, technology will enter this industry soon, the first company (which may not be one of the current players) to offer a modern solution will start the ball rolling and when it happens, I wouldn't want to stand in it's way! It happens in all industries, history has shown those who resist change get left behind, once dominent players cease to exist and new markets emerge! [Look how quickly the iPad / tablets have grown over the last year... or how quickly Nokia went from industry leader to nowhere...]
Many of whom use Hometronic for the heating and HW and write to a set of APIs via an interface, but that is another story you can Google later.
Hometronic will never become mass-market, it's way too geeky... No offence but anyone prepared to enter in 1,600 different on/off times to control their home heating (and/or lighting) needs to get out more!