One of the big divides between professional chefs using sous vide and home cooks is the use of probes with sous vide. The majority of professionals always probe and the majority of home cooks don't. But more and more sous vide cookers are coming with probes, such as the PolyScience HydroPro, the VacMaster SV10, and the Anova Precision Oven, as well as tools such as the MeatStick. So I thought it's important to talk about why you may want to use one.
In general there are several main reasons for using a thermometer when cooking sous vide: HAACP regulations, core-based timing, preventing overcooking during the sear and speeding up the cooking process.