"David" wrote in message
...
I would like to be able to measure the ambient temperature without
carrying a bulky device.

Favourite option would be an attachment to a mobile phone. Why? Well,
because.....

So far I have found this:
https://shop.thermodo.com/
which looks the business but is not widely available.
Around £28.09 in the UK via eBay.

Does anyone of a similar product?
Plugging a sensor into the earphone socket seems a logical design.

The Philips Hue motions sensors have an internal temperature
sensor and you can either read that on your phone or ask siri or
alexa or google what the temperature is. And siri will tell you
the range of all your sensors just by saying 'hey siri room temperature'
or you can ask for the temperature in a specific room. Outside
temperatures too with the outdoor movement sensor.

Not particularly cheap, but on special as cheap as your price.

BUT you need the Hue base as well if you arent using the Hue system already.