I can tell you Apple health app is not accurate on tracking steps and distance traveled and such.
The health app and other motion tracker app which are usually wrong are using apple motion engine chip. I think the motion engine can be accurate, but it needs to be calibrated to your steps and such and it most likely depends on where the phone is mounted. In my case I usually have the phone in my pocket.
Since the Watch is going to use the same motion engine as the iphone 6 it too most likely will need to be calibrated in order to provide you accurate data.
Apple's M7/M8 are quite accurate, as shown in the tests in this article. I've used both the Withings Pulse (worn close to the body in pocket or with clip) and an Apple 5S. Both provide almost identical step counts when worn close to the body. And both are within 10% of the GPS data. One thing I've found out through trial and error is that wearing your tracker or smartphone in way that lets it bounce around relative to your body movements (e.g. inside a loose pocket) will wreak havoc with the activity data.
The problem with step counting via the iPhone is that the charge can't last for a whole day. So when you need to recharge, it will be out of your pocket and stationary on a desk. Your steps will then no longer be counted.
At least with wearables like the Apple Watch, the battery is expected to last a day, so your steps will be counted all the time, giving you a more accurate picture of how many steps you really took over the course of one day. You take it off for recharging at night, a time when you're most definitely not taking any more steps (unless you're sleepwalking, that is).
"the iPhone is that the charge can't last for a whole day."
Huh? With an iPhone 6 Plus over ten hours of active use versus the Apple Watch's 3 or so how do you come up with that comparison? Both devices standby (when background activities such as the Health monitoring continue unabated) hours far exceed a normal day of activity so the odds are quite good both will suffice, though the phone has the edge in total battery lifetime. Which is sort of expected given how much larger either the 6 or the 6 Plus is compared to the watch...
"That means I can rack up the step count by just lazing around."
If only iPhone could discern its own elevation relative to the ground. Any activity below thigh-level height could be discounted. Perhaps a height tolerance slider could be used to regulate the process.
The researchers didn't do a comparison with the accuracy of the results you would have obtained using, say, a Garmin GPS watch with foot pod and heart rate monitor strap. The foot pod, as you might guess, is on your foot. When using the foot pod indoors on a treadmill (and GPS off, obviously), I've found the accuracy very close to the result reported by the treadmill's monitoring. The foot pod gives you distance and stride rate data that you could use to calculate total steps taken, if that's what you want. I just track the distance, time, etc. without worrying about total number of steps. Without the foot pod (or something comparable), I don't think you are ever going to get the same distance/step count accuracy from a wrist worn device (even an Apple watch) or cell phone, regardless of the software. The Garmin foot pod is of no use on a bike, which has its own dedicated device with suitable algorithms for cycling. And of course, you can now get watches which do a decent job of tracking swimming, as well as cycling and running/walking. But I don't think the Apple watch (and the other fitness bands) are aiming at this more specialized fitness market, which has a premium on accuracy of results as they are used a lot for race purposes.
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I can tell you Apple health app is not accurate on tracking steps and distance traveled and such.
The health app and other motion tracker app which are usually wrong are using apple motion engine chip. I think the motion engine can be accurate, but it needs to be calibrated to your steps and such and it most likely depends on where the phone is mounted. In my case I usually have the phone in my pocket.
Since the Watch is going to use the same motion engine as the iphone 6 it too most likely will need to be calibrated in order to provide you accurate data.
Apple's M7/M8 are quite accurate, as shown in the tests in this article. I've used both the Withings Pulse (worn close to the body in pocket or with clip) and an Apple 5S. Both provide almost identical step counts when worn close to the body. And both are within 10% of the GPS data. One thing I've found out through trial and error is that wearing your tracker or smartphone in way that lets it bounce around relative to your body movements (e.g. inside a loose pocket) will wreak havoc with the activity data.
The problem with step counting via the iPhone is that the charge can't last for a whole day. So when you need to recharge, it will be out of your pocket and stationary on a desk. Your steps will then no longer be counted.
At least with wearables like the Apple Watch, the battery is expected to last a day, so your steps will be counted all the time, giving you a more accurate picture of how many steps you really took over the course of one day. You take it off for recharging at night, a time when you're most definitely not taking any more steps (unless you're sleepwalking, that is).
"the iPhone is that the charge can't last for a whole day."
Huh? With an iPhone 6 Plus over ten hours of active use versus the Apple Watch's 3 or so how do you come up with that comparison? Both devices standby (when background activities such as the Health monitoring continue unabated) hours far exceed a normal day of activity so the odds are quite good both will suffice, though the phone has the edge in total battery lifetime. Which is sort of expected given how much larger either the 6 or the 6 Plus is compared to the watch...
"That means I can rack up the step count by just lazing around."
If only iPhone could discern its own elevation relative to the ground. Any activity below thigh-level height could be discounted. Perhaps a height tolerance slider could be used to regulate the process.
The foot pod gives you distance and stride rate data that you could use to calculate total steps taken, if that's what you want. I just track the distance, time, etc. without worrying about total number of steps. Without the foot pod (or something comparable), I don't think you are ever going to get the same distance/step count accuracy from a wrist worn device (even an Apple watch) or cell phone, regardless of the software. The Garmin foot pod is of no use on a bike, which has its own dedicated device with suitable algorithms for cycling. And of course, you can now get watches which do a decent job of tracking swimming, as well as cycling and running/walking. But I don't think the Apple watch (and the other fitness bands) are aiming at this more specialized fitness market, which has a premium on accuracy of results as they are used a lot for race purposes.