Share a sensor

Is it possible to share a sensor. By example I install a hidden sensor on my door and connect them to VMB7IN

If i want to install an alarm system in the future can I use the same sensor. Or have I to disconnect them from the Velbus installation?

It is possible with a workaround, but basically not-done.
You could e.g. add a relay, so that the alarm system is electrically separated from the Velbus system, to increase reliability of both systems.