I’m interesting in doing the exact same thing: adding a simple sensor to my HVAC’s condensate pump to alert me when it’s been running for too long. This thread appears to be quite useful: Internal contacts on ecolink door sensor (DWZWAVE2.5-ECO)
I got as far as buying the Schlage sensor (it has an Ecolink label on the back, model # DW-ZWAVE2), but too many other projects got in the way. I’ll update here if I ever get the thing installed and working. Anyway, hopefully the thread above is helpful.