CCU3 (Link is only in German language available, sorry) or RaspberryMatic (it’s a Raspberry Pi 3B with an extra Homematic module) are Homematic Bridges. You will need one of these two bridges or a CCU2 (old version) to connect the actually supported Homematic devices to Homey. So it’s not possible to connect the door-/window sensor with Homey without one of these bridges.
Btw, this is the official Homematic thread.
