I have a HB-100. Good monitor. Does what it's supposed to. As far as whether you need one or not, I can't answer that. There are plenty of reference posts here on what a HRM will do for you. BTW, I've had my CB-100 for about 8 yrs. Cateye make good products.
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Litespeed, lasts a lifetime.
Specialized Tarmac, lasts a lifetime, or until it breaks.