I bought the Tapo T110 Door Sensor Mini to keep an eye on my back door, and it does the job well. The sensor is genuinely small and discreet, so it fits neatly on the frame. Setup was straightforward once I realised a hub is required, which is worth knowing before you buy. It pairs fine and alerts come through reliably. Only reason for four stars is that you cannot use it standalone, but for the price it is a solid addition to a Tapo setup.