Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Highly Inaccurate

I used to have Polar hear rate monitor, but decided to try this one since it was only around 35 dollars. (So I know how to use one correctly.) Unfortunately, the heart rate portion is highly inaccurate. It often doesn't read my heart rate at all, and when it does is hit and miss. Sometimes it only is reading every other heart beat, so it will read "85 bpm" when it's really around 150, and then for a minute or two it will be accurate.I really wanted this to work, but sorry to say I wouldn't recommend that anyone buy this product for the heart rate monitor portion. I would stick to the Polar heart rate monitors; they were more expensive but they worked like a charm.