After going through two Polars, I bought a Sigma many years ago. It's still working just fine. I use it for the gym. It is a basic HRM, gives you calories burned, etc., but no mapping.

I have a Garmin Forerunning 310XT that is several years old. I recently had to replace the chest strap - even a new battery didn't make it read correctly. I like this Garmin because it's easy to use.