I started P90X with no heart rate monitor.  Then I splurged for a cheap ass wrist watch model that does not use a chest strap. Instead you push a button on the top to get a readout.  That didn’t work very well.  Probably made my blood pressure go up just by trying to get a reading to work. So then I really decided to splurge (for real this time) and bought a Polar FT4.  Not overly excited about the chest strap but it works.  I think I’ll get used to it.  It made a huge difference in the Kenpo last night.  I was able to constantly get feedback on my heart rate and push myself more to get back into the aerobic zone I wanted to be in for this workout.  Very happy about that. Taking Kenpo X to a whole new level now.