Do I need a plug-in/Wi-Fi model or is a battery-powered Bluetooth model enough?

If you only want to confirm whether your home has a radon problem and to verify mitigation after the fact, a battery-powered Bluetooth model (Corentium Home, Wave Radon, Aranet Radon Plus) is sufficient. If you want push notifications, remote monitoring while traveling, or smart-home integration, choose a Wi-Fi model like the Airthings View Radon or View Plus, or a continuously plugged-in Ecosense unit.