Heiman Smart CO Alarm vs Shelly Plus Smoke Alarm

Carbon monoxide monitoring or smoke detection, pick your hazard first: the Shelly Plus Smoke Alarm wins this comparison on price, owner rating, and a wider connectivity spread, WiFi plus Bluetooth for pairing, versus the Heiman Smart CO Alarm's Thread-only radio. The Heiman Smart CO Alarm compensates with a longer rated battery life and a slightly broader integrations list, reaching Google Home, Alexa, Apple HomeKit, Samsung SmartThings and Home Assistant through Matter over Thread, one more platform than the Shelly's WiFi-based connections. As with any CO-versus-smoke comparison, the two do not overlap on hazard type at all: the Shelly only watches for smoke, and the Heiman only watches for carbon monoxide, so many households will eventually want both rather than treating this as an either-or choice. Buyers who specifically need a hub-free WiFi smoke alarm for Home Assistant or MQTT automations should get the Shelly Plus Smoke Alarm, while anyone monitoring a gas appliance or attached garage for carbon monoxide, and who already has a Thread border router, should pick the Heiman Smart CO Alarm.