Activity tracker for use with MyFitnessPal + MapMyFitness?

Hello.

I'm looking into purchasing an activity tracker for use with MyFitnessPal + MapMyFitness. I have my iPhone 6 linked to both of these apps to record steps. I also have MyFitnessPal + MapMyFitness linked. I record all my food/drink via MyFitnessPal and I record workouts (walking, hiking, jogging) using MapMyFitness. I also manually enter indoor workouts (treadmill) as MapMyFitness doesn't really seem to work well with stationary workouts (like the treadmill). And I don't "wear" my iPhone during treadmill workouts, so those steps are lost.

Right now, things are working well and seem accurate. The only "issue" is that I don't always have my iPhone with me, so it's not all that accurate in counting my steps. So, I'd like to purchase a wearable tracker to replace the iPhone and wondering what device MyFitnessPal users would suggest? Would any of these wearables work with indoor workouts (like a treadmill)?

Thanks,
Kristin.