Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Heart rate monitor unsatisfactory

From the day one, heart rate monitor showed erratic number or won't show any number at all. Sent back twice, each time unit passed their test. I've tried everything from placement of chest strap to using gel on the sensor to no avail. Last 2 years heart rate monitor works only 1/3 of the time. I gave up. But it's a good concept if they can make it work right. Apparently this is a common problem by looking at the internet blogs/entries. I'd imagine newer Forerunners solved this problem? Be prepare to return the merchandise, but perhaps, it'll work for you?