How well does it track heart rate for activities such as HIIT or Crossfit?

For me, the primary use of this product would be during weight lifting, HIIT, and Crossfit style workouts. During, let's say, a HIIT workout, I may be in range of my phone and then head out for a quick run and then be back in range. So how quickly would it sync back up? And then, as the question states, how well does this product work with workouts that don't necessarily involve running or cycling?

Wahoo TICKR X Heart Rate Monitor

Wahoo TICKR X Heart Rate Monitor

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