Modify Ring Contact Sensor in a series of wired security reed switches
Hopefully this will help someone else. I just spent three evenings working on this. Wanted to use my existing wired sensors and have all the Ring contact sensors centrally located (in the closet of the old alarm system box). Here's what I have learned:

You can attach wires across the magnetic reed switch however this only works with a very limited wire length to the existing wired contact sensor. In my experience wire lengths of less than 20 feet work although not reliably and one wired sensor would not work with a wire >2 feet.

On the Ring sensor PCB, there is a spot for a surface mount berg header. See picture (JP1):


From other posts and my own experimentation, JP1 pin outs are as follows:


Pin 1 (+) = Battery 
Pin 2 (G) = Sensor Ground 
Pin 3 (V) = Active input, 3V=Closed, 0V=Open 
Pin 4 (C) = Normally Closed input 
Pin 5 (O) = Normally Open input


In my experimentation the "C" and "O" inputs are no better than soldering a wires across the magnetic reed switch in that only very short runs to the wired contact switches work.

Best solution is to put a 1M Ohm resistor from "G" to "V" and connect the wired contact switch across "+" and "V". The 1M Ohm will minimize the battery drain (less current than what flows through the internal resistance of the battery) but provides the needed pull down to activate "Open" when the wired sensor opens. With this configuration I have wired contact sensors working reliably with >50 feet wire runs and one Ring sensor with 4 wired contact switches (my basement door and windows) connected in series.

Be careful soldering to these pads. The pads are surface mount and it is very easy to lift the pads once wires are soldered to them. Strain relief attached wires!

The "V" active input opens the door (pun intended) for a lot of other potential uses. Could be used attach/monitor an existing glass break, water or other sensor not available from Ring with some simple modifications to the other sensors.

Enjoy and good luck!