Is it possible to have a door contact Arm the system when it it Closed and Disarm the system when it is open?
You could do this in Rule Machine.
Use 'door contact closed' for the trigger.
Add an action for "Control HSM/Garage Doors, Locks, Valves, or Thermostats"
Select the mode you want to set from the drop-down
You could use a separate rule to disarm, or add two more actions:
Action 2: Wait for event: door contact opens
Action 3: Disarm HSM
I'm assuming this door sensor isn't a perimeter door that HSM is monitoring, since that would defeat the purpose of having a perimeter door sensor.
So In the case of a break in, If I open the door, the system is disarmed?
Yes, you are 100% correct. This just temporary I want to find something that has a set of dry contacts, when there is a dead short the system will arm and on an open it will disarm. This will open a great deal of much more secure opportunities. When I find this device I can hook up my DMP alarm system it along with Safety Monitor. FYI DMP alarm system is just like a system from ADT (Ademco) just much more advanced. Using Hubitat gives me some advantages it can not do.
The Zooz ZEN 58 (D.C powered) or ZEN 57 (A.C. Powered) have a dry contact output and a separate dry contact input.
I use one to convert a dry contact output from a voltage sensing device into a Z-Wave signal from the ZEN 58 input, which then controls a rule in the HE depending on state of dry contact.
I didn't want a battery powered device so the Zen58 fit the needs 
There is an economical contact sensor with a set of dry contacts built in, but I can't recall the product name unfortunately. It has been discussed here
maybe you can locate on ebay
