There isn’t any option or device within Tado to detect if the room is occupied or not, however you might want to consider a Smart PIR that works with IFTTT and you may be able to setup an Applet that will switch the AC on or off?
I don’t have an AC controller just yet so I am not sure if they have a system that is present on the Thermostats whereby if a window or door is open that changes the room temperature it shuts off the heating for a period of time?
We looked into this at length, but found it to be too error-prone when implemented on the Smart Thermostat or Smart AC Control directly (as it would have to face the AC and the whole room simultaneously). Instead, we opted to ensure compatibility with other platforms such as HomeKit, IFTTT etc, so you could use a compatible contact switch or PIR sensor and set up a rule to then turn the AC off, for example.
In theory you could use HomeKit compatible presence sensors. I believe there is a company doing some based on Apple's iBeacon technology. However apparently early efforts were not precise enough in terms of location tracking so as to do room level tracking. Not sure what the current state of things is.
I also found the following which is more like a traditional PIR sensor but a lot smarter. See -
Note: Motion sensors are different to presence sensors.
See also the following.
They seem to be claiming they are more precise and hence can accurately track per room presence.
For heating (a house) presence detection does not need to be room level precise but your requirement for AC control might benefit from room level control.
Open door or window sensors is in comparison dead easy. There are plenty of HomeKit compatible door sensors like this one (and many others).