I use this unit daily to monitor blood pressure, and I have compared the results to multiple Doctor's (old-fashioned) readings as well as machines in pharmacies and medical offices. It is accurate. Usually it is spot on, within 2-3, and any differences were not statistically significant. This model also has a feature that allows you to average out three readings in a row, which should help offset any inaccurate readings.

As with any blood pressure monitor, you should check it against other monitors when you first get it to make sure you are getting accurate readings. There is a specific technique to using a wrist monitor, whereby you are to hold the arm from which the reading is being taken still with your wrist at heart level. There is a beep indicator that lets you know when you are in the right spot, but it is your job to keep your arm there during the reading - best to hold the elbow of the arm that has the device on it with your other arm.

As to the reviewer that got a defective unit - that is unfortunate - but it should not influence people's buying decisions on this model. There is the potentiality to get a defective unit when you buy any kind of device.

The best thing for me about this unit is that it is extremely portable, and easy to take with you when travelling. Highly recommended.Get more detail about Omron Deluxe Wrist Blood Pressure Monitor with APS HEM-650.