The fitness band, the smartwatch and the phone in your pocket: what each truly measures

The wearable market sells you the same sensor twice at ten times the price, and the difference between a good band and an expensive watch is smaller - and in a different place - than any launch keynote claims. This desk tested step-count honesty on its own stairs, so it can say the following with numbers behind it.

What the cheap band does at parity

• Heart rate at steady effort. The optical pulse sensor is the same physics at both prices, and during a walk or a run at constant pace, a good budget band tracks a chest-strap-grade watch within a few beats - it is at intervals, arm-swinging irregularity and cold skin that the cheap window drifts.
• The alarm on your wrist. The sleep-stage numbers are entertainment, and both tiers produce the same entertainment; the genuinely useful sleep feature is the vibration that wakes you without the phone across the room, and no tier does it better.
• Step counts, at the same ratio: both over-count while brushing teeth and under-count while pushing a stroller. For "more yesterday, tomorrow", either is honest enough - which is the only thing step counts were ever for.

Where the premium actually buys

GPS without the phone is the honest dividing line - a watch with its own receiver maps the run while the band needs a shoeing phone in pocket; if you run free-handed, that is the purchase, full stop. After that: screens you can read in equatorial sun, cellular and contactless payment for the phone left at home, and training-load software for the second sport you now do. If none of those five describe your week, the band is the right size of wallet.

The phone you already own is the control group

Phone-in-pocket step counting is the reference these devices beat or match; and the phone's heart-rate absence is genuinely the one thing it cannot substitute. Before buying anything: walk a measured distance with the phone's app, check its number against the map, and ask what a wrist would change - usually the answer is "the pocket emptying at 5am", which is a real answer, and exactly the kind this desk prefers.

The habit both tiers share

A wearable changes nothing about the body; it changes the record. The only evidence-backed loop is: consistent time, a target you can see on a grey morning, and the streak you protect. Choose the device whose numbers you will actually look at daily, because the entry-price band with a daily habit beats the flagship in a drawer - and the desk's own stair test stands behind that sentence more than behind any spec sheet.