You don't need to replace them. Just get a single EcoLink FireFighter wireless audio detector, and mount it within 6 inches of any one of your Kidde smoke/co detectors.
The Ecolink FF (costs ~$35-40) is a z-wave device that specifically detects smoke/CO alarms. It pairs to the Hubitat as a z-wave device and can be used as a trigger upon detection of smoke/CO alarm audio.
Because the Kidde detectors are wirelessly interconnected, when any of them is triggered, all of them start alarming, including the one that is adjacent to the Ecolink FF. So, you need only one of them.
I purchased one of these when I moved from Wink to Hubitat. It has worked flawlessly. I check my Kidde Smoke/CO alarms once every 2-3 months. On both occasions, rule machine automations that are based on the Ecolink FF being triggered have worked flawlessly.
