1. Easy to add three detectors to my Nest account. 2. Intelligent automatic setup. 3. Simple to do monthly test on my phone or tablet via the Nest app. 4. Status of each detector available via the Nest app.
These devices from Aqara (Xaioma) work great and integrate easily with Home Assistant and other hubs. I will continue to recommend and buy these as long as they don't take the Apple approach of locking everything down.