Otherwise, you'll struggle to spot the hardware differences between the two models, and it's likely that there won't be any big changes internally. As 9to5Google says, the best we can hope for is the inclusion of NFC (for mobile payments) across the range, which was only available on the special edition Charge 3. That and, perhaps, an always-on display, if Fitbit have been able to improve battery performance sufficiently.

The only other thing that's likely to change is the price, with the leak suggesting that the Charge 4 will cost £10 more -- the leaked listing was from the UK -- than its predecessor. If Fitbit is planning to use Fitbit Pay as the lever to persuade folks to spend a little more, it might be a tough sell in these straightened times.

And, at the risk of soapboxing, it's hard to see -- short of GPS -- what features Fitbit could add to the Charge 4 to make it noteworthy. As we explained last year, the technologies included in almost all smartwatches are now so common, and interchangeable, that it's increasingly difficult to stand out.