I use a Polder unit witha probe that fits through the vent of my CS. It gives the current meat temp, an alarm for when it reaches the desired temp, and has a timer alarm. I am on my second one in about 12 years (the first still works but it is a little worn looking and It doesn;t stand up anymore!). Mine have been very accurate.
I also have a NU-Temp 701 for remote use. It is not as accurate as the Polder, and, I do not use it much.
For instant reading of temperature I have a Thermopen.
All obtained through the internet.