An arm blood pressure monitor features a cuff that is placed around the bicep and automatically inflates to determine blood pressure. Arm monitors are usually more accurate than other types of monitors and can alert you to especially dangerous readings.
A wrist blood pressure monitor includes a cuff that fits around the wrist. Wrist monitors tend to be smaller in size, but they are usually more comfortable for the wearer. However, a wrist monitor may not be as accurate as an arm monitor.