So I need the PEK to run my ecobee?

Hi Team, I have a Honeywell thermostat that I would love to replace with my new bought ecobee3 light.

I can’t find any module/furnance in our house, attic, or crawl space. We just have a big Goodman unit out of our rental house.

Can you tell me if I need that PEK in general for that setup?

Thank you