Homekit and different systems

Not sure where this should be posted, but thought i could start here.

I am looking for some knowledge of HomeKit here. My plan is to purchase some room temp sensor from one manufacturer and outlet controllers from another manufacturer to help control heating in a couple of difficult rooms.

For example, I am looking at the Ecobee 3 for temp monitoring and the Elgato Eve Energy to control the on/off functionality of some space heaters. Then I am hoping that HomeKit can monitor the temp sensors and turn the heaters on and off as needed based on the info from the temp sensors. And I would love to take this one step further and have the heaters not be running when the main furnace is running, or possible when the attic fan is running. Is this possible for HomeKit? Or do I need to use something more like IFTTT? Or do i need to invest in a more integrated like a z-wave or Insteon.

I am hoping that HomeKit can fill the void I have but I don't want to purchase separate systems and not have the desired functionality.

Hopefully this all makes sense to the HomeKit gurus out there, and any help or suggestions are greatly appreciated.