In recent tests, different models of smartwatches and fitness wristbands reduced the battery life of the connected smartphone. Depending on the product and the phone this was in the range of two to eight hours of reduced usage time. Having the smartphone run for only half a day until it needs a new charge is not ideal and this is likely to put off most users who use smartphones without an exchangeable battery.

Of the devices that were tested, the battery life could last up to five or six days. However, as consumers add more devices to their households the number of gadgets that need to be charged is expected to reach a point where it becomes a burden for the consumer. Here the discussion arises again of the trade-off between design and usability — a more efficient battery would likely not allow for a light and sleek design — and yet a desirable feature for a smartwatch would be a battery that lasts for several months.

"We are currently seeing two opposing trends in the market with regards to form factor evolution. On the one hand there are vendors offering smart wrist-wearables in a familiar watch-like form factor," said Ms. Zimmermann. "On the other hand in the past six to nine months, we have seen vendors launching products that resemble the early fitness wristbands, but come with displays that add significant functionality, including message and call alerts. These cross-over products are generally marketed as fitness devices, but with the strong slant toward the communication aspect."

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