Polar S725X Monitor Learning About Polar Monitors Heart and Pulse monitors are becoming not only very popular for cyclists but also a necessity for many. … As great as they both are, the S725 does have a few advantages worth checking out such as the target zone with is shown as a percent of max bpm, it’s water resistant to a greater distance that the S720i and has mobile connectivity. There are also more running feature options with the S725. As I’ve said, however, …