Product review (5 stars): Works great!
I had a faulty thermostat and the manager of my apartment building had it replaced. However, they switched a very modern, digital thermostat for a bare-bones, analog one. This means I can't see the actual temperature. Therefore, I needed something to make sure the new thermostat was working properly and that the house is at the temperature it's supposed to be.

It's as easy as opening the packaging, putting the battery in, and it's already working!