Teardown: Fitbit Sense smartwatch

In mid-January, Google completed its $2.1bn (£1.5bn) acquisition of Fitbit, the wellbeing and fitness wearables company. Fitbit’s Sense smartwatch, launched last August but significantly upgraded several times since then (including the addition of Google Assistant), highlights several interesting aspects of the deal. Two stand out.

First, to get regulatory approval, Google has made various international commitments over how Fitbit-derived data will be used. The EU has secured a renewable block on its use to inform Google ads for 10, potentially 20 years. It has also received guarantees on Fitbit device interoperability with other wearables and, perhaps most important, the controls users have over what information can and cannot be shared for any purposes.

This latest generation of wearables continues to get closer to its owners. Sense adds stress management and blood oxygen-level analysis (while sleeping) to a familiar raft of features that includes GPS exercise tracking, electrocardiograms and water resistance (to 50m depth). With all these feeding a trial six-month subscription to Fitbit’s premium services, one initial criticism of Sense has been that its associated apps overwhelm you with information. Indeed, sceptics note, but what about an AI?

The second aspect is that the deal once more finds Google reaching outside its own huge engineering base to acquire hardware and industrial design innovation. The company’s efforts have been improving but as it acquired the handset design team of Taiwan’s HTC to close the gap with Apple and Samsung, it now hopes Fitbit will help it challenge the same companies in wearables more aggressively.

Sense also sees Fitbit playing catch-up in a product category where it was a pioneer. It is the company’s flagship competitor to the Apple Watch 6 and the Galaxy Watch 3, priced at a comparable £299 and looking to get consumers to ultimately trade up to around £8 a month for its premium services. This explains the rich feature set, and Fitbit’s work on continuously upgrading Sense’s capabilities.

The stress-management feature is timely, whether by accident or design. It combines data derived from established wearable features such as the ECG and temperature sensor with electrodermal (EDA) information.

The EDA data is acquired through two brackets alongside the touch-sensitive controls on either side of the Sense. When you cover them with your watchless hand for a couple of minutes, they measure the impact of sweat on the conductivity of your skin, an indicator in turn of how much adrenalin you are producing.

Not surprisingly, an iFixit teardown found that the Sense has a very compact design. Its extra features – e.g. the red and infra-red sensors needed for blood oxygen SpO2 readings – mean that it weighs slightly more than other Fitbit products such as the Versa 3, but it comes with an easily detachable infinity band that allows it to sit easily on the wrist normally and during exercise.

Regarding the physical assembly, iFixit found it less complex than the latest Apple Watch, with the main motherboard doing a lot of work in a basic form factor. But there are some design concerns.

Entry around the display involves getting past a fair amount of glue with a heat gun and steady hands. “The display-first disassembly procedure means screen replacements require only a few steps, but those steps are difficult and can easily damage the display,” iFixit notes. This is a bit of a warning for anyone who has found that exercise and smartwatch fascia can involve the occasional bump.

Fitbit has also glued some of the sensors underneath the battery because they need to face the outside of the Sense, with the battery itself attached to the motherboard. Repairs here are again potentially awkward, leading to an iFixit score of 5 out of 10 for repairability.

There have also been some trade-offs on the specification. The battery is rated at 1.02Wh, which is less than 1.17Wh for Watch 6 and 1.3Wh for Galaxy Watch 3, but claimed life is up to six days between charges (though using a reasonable raft of features does bring this down to between one and two).

There is some clever system design going on, but processor responsiveness to swipes and taps can, some early users say, be a little unpredictable.

Fitbit has historically guarded detailed processor specifications. The Sense is thought to have had an upgrade against the Versa 3 but still one based on one of the more power-efficient Arm Cortex cores.

Sense justifies its price and position in the market, although there is room for growth (and to be fair, wearables is itself an evolving segment).

Google’s resources will give Fitbit the chance to invest more in silicon non-recurring engineering, so that its own processors are a closer match for the custom implementations of its main rivals. Apple has also taken a lead in building out apps around Watch, so there is scope for Fitbit to improve its offering there.

Looking both to today and the future, it is fair to say that Sense makes sense.

Key components: Fitbit Sense

Exploded view

1. Side assembly

2. Battery

3. Motherboard

4. Vibration engine

5. Side assembly

6. Electrodermal bezels

7. Rear incorporating sensors

8. Front and OLED display<''>Motherboard

9. GPS SoC, MediaTek

10. Processor, Fitbit

11. Flash memory, Kingston