On my ride today, the 705's heart beat didn't start to register until maybe six miles in... I repeatedly adjusted the strap and wet the sensors... it was making good contact. But it wouldn't work. Finally, it started to register but even then, it sometimes fluctuated wildly.... not my heart.. the display.

I'm wondering if my mobile phone (iPhone) somehow interferes with it? In my first ride with this new unit Wednesday, the phone was in a bag on the back. This time, it was in my jersey pocket not far from the strap. Anyone else experience this?