The Viiiiva 4iiii HR monitor is a really cool concept. It connects via Bluetooth with your iPhone to send HR data from the strap itself, but also collects data via ant+ and sends data to iPhone from your Garmin footpod, cadence sensor, or Garmin power meter as well. I was hoping that for $80 it would overcome the limitations of the Garmin HR monitors, where they don’t work great until you start sweating, but alas, it has those same limitations. I mainly used this with my heart rate variability app called ithlete and occasionally with my Garmin 310xt when running. I have since started using the ithlete app with the ithlete finger sensor; it gives better, more consistent results.