6 fitness trackers that do something different — including the viral retro Casio with hidden depths, and a tracker with a 400-day battery

Today's best smartwatches are ultra-capable, feature-packed powerhouses.

But is it just me, or are they all starting to feel kinda samey? Casio recently made headlines with its delightfully retro F-B100W , which takes your classic, rubbery, blocky Casio watch and adds in step-counting features.

That sent me off on a hunt for other smartwatches and fitness trackers that do something a bit different, and I was not disappointed with the results.

I've rounded up my favorites below.

There's the new-out Huawei Watch D3 , which looks like your standard, modern smartwatch, but has a secret, in-built blood pressure cuff.

For those who prefer a traditional watch aesthetic, there are the Garmin Instinct Crossover and Withings Scanwatch 2 , both of which have smartwatch features but also mechanical hands.

Neither is especially new, but both have maintained popularity by their seamless blending of digital and analog.

Finally, a couple of especially intriguing options from outside the big watch brands.

The Jaye band is an ultra-minimalist smartwatch that displays only the most important notifications on its tiny screen to minimize distractions.

And then there's the LightInk , which can run for an absurd 400 days on a single charge.

Such a lengthy runtime is achieved by adding solar charging, swapping your average vibrant AMOLED display for a low-energy, monochrome e-ink one, and stripping the smart features right, right back.

It's open source, so with the aid of a 3D printer and a few basic components, anyone could own one.

Scroll down for a closer look at these weird and wonderful smart trackers — hit the View details button to learn more about each one.