@Wayne-TP 

Thanks for your answer. The alarm event, or even notification event, seems so obvious to me that i didn't check before buying the smart button wether it was possible or not. I discover it is not possible ... So i search how to use the button as a mechanism to activate the alarm when the last person is leaving the house, and activate it when one is coming back.
The only way i found is to have the alarm always on and activate or deactivate with the button the confidential mode. Which is frustrating since when we are at home the camera is no more caputing any movement around the house which could be usefull if any event happened that need to get some record ....
It seems so obvious to me .... why not having this ?

Thanks.

  @Piemil You could probably use Home Assistant for that, but it requires some skills and a platform it runs on (Pi for example).

  @hankybanister 

Thanks but i bought a button and a hub for 35€ just to activate the alarm when i am leaving home ... i wont build a Google IT infrastructure for such purpose. And since the possible activation for the camera are "movement" "play a tone" ... why not having "alarm on/off" ??? 
It seems obvious.