Zx: Heart Rate Zones Training

I was looking for an interval timer for my own HIIT training that could also pair with my coros armband to show my heart rate. Paying $14 for this app seemed like a no-brainer when the cheapest watch I could find to show my heart rate was $180. Now I get to see my interval timer and heart rate in the one place. It works perfectly with my coros armband and make sure I stay in the zone during night intensity intervals (while not pushing too hard above my range). Thanks for making such an intuitive and affordable app with great functionality.

App is promising. While running and cycling work fine, logging a swimming workout fails. It says "Please allow Zx to 'Write Workout Data' in Health and try again. By the way your support website is just a placeholder site. Might want to update that. In addition to the above bug, to be useful during swimming, the alerts would have to be different patterns for above and below zone, and they'd have to be constant. For example, short quick vibrations if below zone and long slow vibrates if above zone. The same kind of constant and differentiated alerts would be useful in other situations (e.g. watch under your sleeve or glove) but especially in swimming when it's not practical to look at the watch face during a lap.

4 stars. Would give 5 stars if the colored bars in the workout graph also displayed the target heart rate zones like the Polar Beat app. does.