When it comes to under desk treadmills, there are a few extra features that you might want to consider. These include a built-in fan: this can help to keep you cool as you walk or run, and can also be a great way to circulate the air in your office; a display screen: this can help you to keep track of your speed, distance, and time, as well as calories burned; a heart rate monitor: this is a great way to make sure that you are staying within your target heart rate zone.