The majority of clinically validated monitors are upper arm monitors, where the cuff is put around the arm, above the elbow.
However a number of wrist monitors are now clinically validated, but readings at home may be inaccurate if the wrist is not held at heart level. Just a small difference in the height of the wrist monitor (relative to the heart) can make a big difference in the reading you get.
For this reason, the British Hypertension Society recommends the use of upper arm monitors in preference to wrist monitors.
All Blood Pressure Association monitors are upper arm home blood pressure monitors.