I have been testing
Hue Motion Sensor (~£29) on Hue v2 Hub - using cocohue App
Hue Motion Sensor (~£29) on HE C7
Sonoff SNZB-02 (~£12) on HE C7
Tuya Temp and Humidity Sensor (~£14) on HE C7
Secure SRT321 Thermostat - (~£65) on HE C7
Aeotec AERQ Temp and Humidity (~$30) on HE C7
Aeotec Multi Sensor 6 (~$39) on HE C7
Two factors play in these sensors, ability to reliably, consistently relay temp readings AND Battery life.
For reliability/accuracy the following did well
Multi Sensor 6
Hue Motion Sensor on Hue (not on HE direct)
the Sonoff was highly unreliable as is the Hue Motion Sensor directly on HE C7 (could be MESH related) but other zigbee devices were reliable on the same mesh.
Then Battery consumption.
The Hue Motion Sensors on Hue Hub far exceed everything else on battery - out of 30 Hue Motion Sensors they all last 2 years and report like clockwork on two AAA or 2 AA batteries.
The Aeotec MultiSensor 6 can run on USB power so will run for ever.
Because I had 10 SRT321s and while reliable their battery life was not good, so have converted them all to USB battery eliminators and now they are solid and run forever.
The TUYAs are doing exceptionally well - very impressed by them.
The AERQ's too soon to tell, but two of the AERQs lost all their battery (supposed to last 2 years) during inclusion into the the HE C7 and at £5.99 are quite expensive.
The Sonoffs are burning through batteries and largely unreliable.
The Hue Motion Sensors on Hue Hub - the absolute best by a long way for reliability and battery consumption. Fo the price of £29 you get a lot of sensor for a good price.
The TUYA are proving to be very good for reliability and battery - so if I did not already have a lot of Hue in the house and the Hue Hubs these are what I would go with and at £14 each a good price.
The AEOTEC AERQ is the best priced runner up for ZWAVE, unfortunately the built in Driver does not support offsetting the Temp in the Driver so unless a Community Driver comes out you can't fine tune it. The AERQ also has a nice add on of a Dew Point estimate that is not supported by the built in driver.
ONES TO AVOID
Sonoff Temp Sensor - cheap - with a cheap build that makes it too easy to break when pairing.
Hue Motion Sensors on HE C7 - not a good choice and only really viable if you need direct Motion Sensing which does work OK but the temp reporting does not.