So, with permission from dman, I was able to get his contact group app updated to track how many sensors are open/closed.
The device will show how many sensors are open/closed. The sensor itself will show open when any monitored sensor is open and closed when all contact sensors are closed.
I've only did some quick testing, so let me know if you use it and it goes weird.
In action (I just opened a window and closed it to show the updates):
I used the actuator capability, so you can use any of the states in RM:
Child Device
https://raw.githubusercontent.com/FriedCheese2006/hubitat-contactgroups/master/VirtualContactGroup.groovy
