IFTTT (If this then that) has added support for Cortana so you can now use Cortana to control almost any smart home activity. The service enables you to create trigger phases for Cortana that can then control anything service supported by IFTTT.
So you could set up “Hey Cortana, turn on my living room lights” and then Cortana could turn on your Philips Hue lights. Or you could ask Cortana to boost your hot water via Hive, or lock your door via a smart lock. I even have Cortana setup to lock my car remotely. Having the IFTTT integration means that Cortana can just about do anything you want as it serves as a trigger to any IFTTT supported action, of which there are hundreds. Most smart home services support IFTTT as does Facebook, Twitter, Gmail and many others. There is a really a hell of a lot you can do with IFTTT and having Cortana as the voice input really opens up Cortana’s capabilities.
To get started go to IFTTT and connect up your Cortana service.