The slim and lightweight design of this heart rate monitor makes it comfortable to wear.
Polar made this model waterproof. You can wear it during swim workouts and still get accurate readings, and the water will not damage the mechanisms. This feature also means the T31 will repel sweat. Even the most intense workouts will leave the screen readable and the circuitry dry. The T31 will work with nearly any enabled elliptical, stair stepper, stationary bike or other pieces of cardio equipment, we found in our research.
Elastic straps on this unit are individually coded, meaning they will only pick up and transmit your pulse rate to a nearby Polar chest strap heart rate monitor or compatible gym equipment. In the past, many similar units picked up signals from others and caused cross-talk between the devices. The long-lasting battery gives you 2500 hours of service.
Unfortunately, the battery is not user-replaceable. You have to throw the unit away or recycle it, and get a new one when the battery dies. However, some users report the unit battery lasting up to five years. Also, no battery means a more comfortable ride because there is not a piece sticking out for the battery compartment.