The difference between a smart home that feels magic and one that strands you in a dark bathroom is presence detection.
PIR motion: the workhorse
A Motion sensor sees moving heat. Cheap, instant, years on a battery — perfect for hallways, garages, laundries: walk-through spaces where "movement = occupancy" holds.
The couch problem
Sit still reading and PIR decides the room is empty. Lights off, wave arms, repeat. Anywhere humans are stationary — lounges, offices, bedrooms — PIR alone fails.
mmWave: actual presence
Radar like the Aqara FP2 detects breathing-level micro-movement. The FP2 maps a room into zones (desk vs couch vs bed), tracks multiple people, and runs fully local over your lan. Mains-powered, pricier — that's the trade.
The pattern that works
PIR in transit spaces, mmWave in living spaces, door sensors arming the logic. Our Presence kit bundles exactly that for one room done properly.
Skip the shopping list: the Presence Kit bundles the tested gear from this guide — cheaper than buying the parts separately.