Hunter Fan - Thermostats - Comfort Saver 7 Day Programmable Thermostat with Room Control™ - 44668 for $39.99
Lets you monitor or control temperature in a different room from your thermostat. You can control the temperature using the thermostat, the remote sensor (which you can carry with you) or the average of the two.
Despite the so-so reviews in Amazon, I have 3 of these (it saves rewiring thermostats) & they work fine.
I suggest downloading the manual from here:
as the manual in the units I had was out of date