Was contemplating trying to monitor the flow temps at various radiators in Home Assistant.
Found these pipe clamp temo sensors: Salus PS600 Smart Pipe Temperature Control Sensor only £22.91 (ecowizard.co.uk)
Looks like they may be compatible with Zigbee2MQTT and not (yet) ZHA.
Salus Pipe Temperature Sensor PS600 Zigbee compatibility (blakadder.com)