Most people that use the Apple TV (2015) have it connected to the TV in the living room or bedroom at some corner or along some wall of the house. However, you can also use it just as a pure Wi-Fi to Bluetooth bridge for those HomeKit devices which are Bluetooth based, like those from Elgato.
Once we moved the Elgato Eve Room to a different room at the edge of the house, the Elgato Eve Room was too far away from the iPad Pro to be able to connect over Bluetooth and the Apple Home App lost connection to the Room sensors.
We then simply placed the Apple TV (2015) in the center of the house, connected it to an AC power outlet, and did not connect it to a TV. The Apple TV (2015) was able to find the Elgato Eve Room using Bluetooth, and the sensors could pass data back to the HomeKit servers again through the Apple TV's Wi-Fi connection.