A meat thermometer is a device that can be left in food in the oven, the thermapop is not a meat thermometer because the plastic casing and electronic are not oven safe. If you put your thermapop in the oven and left it there you'd destroy it. You could use it to measure air temperature outside the oven without a problem, although you'd use up the battery quickly if you left it on constantly.
The two most widely available meat thermometer types are mechanical ones which stick into the meat and have a dial you can read, and electronic ones which have a probe on a wire which goes into the meat in the oven. Either type can be used to measure oven temperature, you just put the probe in the oven without being in meat.
Given how dirt cheap oven thermometers and room thermometers are these days there's not much net gain though, you may as well invest a small amount of money in the right tool for the right job.