Polar HRM's are designed to be EKG accurate. Polar HRM's use a waterproof chest transmitter to pick up the heart rate. Battery life is estimated at 1.5 years on the watch and 5 years or 2,500 hours on the chest transmitter. Watch batteries are standard 3 volt lithium and may be changed by a jeweler. Polar will also change batteries plus extend a one year additional warrantee on the watch.
Watches have a one year warrantee, transmitters a two year warrantee.
The chest transmitters weigh only 2 ounces, are molded to the shape of the chest, and are quite comfortable with a one size fits all expandable elastic.