I use a Wahoo Tickr-X for virtually all gym activities, weights, cardio, and classes, and it never misses a beat. Beautiful data. For less strenuous activities, or impromptu thoughts, like A hike along a trail I didn't know existed, or Mall Walks, I use a Scosche Rhythm+, probably the very best optical heart rate reader out there. I've used these two with Suunto's, Garmins, and now the Apple watch, and yes, I do have to reconnect each time I put it on, but it's a simple procedure, and I'm in the Bluetooth area of the watch anyway, connecting whatever headphone/earbuds I have on at the time, so it's a non-issue.