I purchased a Chamberlain CWA2000 driveway alert system. There are no external contacts available, so I took it apart to find a way to integrate with ST.
I ended up tying an Ecolink contact sensor in with the indicator LED on the receiver. The LED goes out when the sensor is triggered, regardless of the volume level on the beeper. Connecting the dry contact sensor directly across the LED terminals does the trick. I then set up a CoRE rule to notify when the contact closes.