The ThruMometer from Blichmann engineering is a great way to monitor wort temperatures as it leaves your counterflow wort chiller. Attach a short piece of 5/16" id or 3/8" id tubing from your chiller to the ThruMometer. Then attach another piece from the ThruMometer to your fermenter.
As wort leaves the chiller it will enter the ThruMometer giving you the exact wort temperature. This allows you to tweak the water flow on the chiller to get your pitching temperature.
Heavy duty, well made and easy to clean. It reads between 88 and 58 deg F.. Eight inches in length. Built of corrosion resistant aluminum and will last a lifetime.