Kind of a bug "it depends." The basic heart strap is $40; the heart strap with sensors for running dynamics is more, it costs $50 bundled with the watch; the heart strap for swimming is $100; the one for triathlon is $130. A power meter can be anywhere from $400 to $3,500 depending on your requirements, some of them also act as a cadence sensor and then you just use GPS for speed. Otherwise the speed and cadence sensor is maybe $50 on Amazon.