Tying into existing standard smoke detector wiring to make it zwave

My home has 8 existing standard smoke detectors (one in every room, hallways, and main areas). They are both battery and A/C powered, and they have a third wire that interconnects all of them. Thus, if one goes off, they all sound. I recently had one fail, and replaced it with this equivalent Kiddie model.

Replacing all eight with stand-alone z-wave-based units would be costly (both in terms of time and dollars). Has anyone ever considered tying into that third cable to determine viability to connect it to a dry-contact z-wave switch like the REMOT-ZFM-80.

Barring any comments from people who’ve already attempted (or completed) this mod, I will start testing to see what voltage exists on the third wire when the state changes from alarm to no alarm.

Never mind. I just realized SEARCH is a powerful tool. Found this thread.

One of these: Kidde SM120X Smoke Detector 120V Hardwired Relay Module
and one of these: Schlage RS100HC V N N SL Home Door and Window Sensor

and you’ve [url=http://forum.micasaverde.com/index.php?action=dlattach;topic=15334.0;attach=10666;image]Z-Wave enabled a standard hardwired smoke alarm/url.

Thanks - got the relay on order, and I’m actually going to use a spare DSC alarm window sensor for the z-wave input. I just removed the magnetic reed switch, and soldered on pigtail that I’ll connect to the output of the relay. Should be a perfect fit.