There are meat thermometers specifically designed to be left in the meat as it cooks. Some are mechanical thermometers that have a dial and can be left in. Personally, if I am going to use a meat thermometer that can be left in the meat, I use ChefsTemp Quad XPro Alarm Thermometer. This thermometer is designed to leave the probe in the meat and has 4 probes with extra-long leads which attach to a temperature sensing head you are able to affix to the outside of the oven via magnets, or use the kickstand and set it on the counter. It has an alarm to notify you when the meat reaches the desired set temperature.