An ECG front end detects and removes the interference that distorts heart rate readings, so your trace follows your effort through intervals, sprints and long steady-pace sessions. The new chest strap construction shields the signal from static noise, keeping readings stable from the very first minute. High-resolution beat-to-beat R-R data is also what makes real-time ZoneSense possible on a compatible Suunto watch.

At 13 g and 36,5 x 36,5 x 8,5 mm, the transmitter has a slim profile that sits close to your chest. The soft strap and silicone grip hold their position through sprints and descents, so the strap always stays in place and your focus stays on the session. Around 460 hours of battery life from a single CR2032 cell make maintenance almost non-existent.

Paired with a compatible Suunto watch, a six-axis motion sensor measures cadence, ground contact time, vertical oscillation, flight time and left/right ground contact balance, so you can see how your form holds up as the pace rises and fatigue sets in. Up to 20 hours of continuous R-R memory stays on the strap itself, and the watch reads it back via timestamps to complete the log after reconnecting.

Connect it to up to three devices at once via Bluetooth. Your watch records the session, your bike computer shows live heart rate and your phone runs the app alongside the other two. Every device receives the same live data, so a long ride or a triathlon brick session runs from start to finish on a single pairing.