This is my first winter in my new house. One project for next year is
going to be heating and insulation, but I want to get a baseline this
winter before making any changes.

I want something that can measure temperature in multiple rooms and
log readings to a central point. I've seen these wireless sensor tags
that look just the thing:

https://wirelesstag.net/

But there are a few downsides with these:

a) They're from a US company, which might be a problem if they don't
work as I might not be able to return them.

b) They seems to use some sort of proprietary RF protocol to
communicate between the tags and the "Ethernet Tag Manager" hub. At
least I can't find any details of the protocols used.

c) The reviews on their forum are very mixed, with some people saying
they work great but other people can't get them to work.

Has anyone got any recommendations for multiple room temperature
measurement with central logging?