FitBit blends wireless, MCUs and MEMS with online interface

The FitBit personal fitness monitor combines wireless, MEMS and cutting-edge algorithms and packaging to keep us in shape, but behind its sleek design are lessons for any designer and aspiring inventor looking to turn what seems to be a simple idea into a truly viable, competitive end product. From conceptualization and market differentiation to component selection and system design, the FitBit is an intriguing study in design choices and consequences.

The device itself records the day’s movements using 3-D motion sensing combined with the company’s own proprietary algorithm. Then, when the user comes within 15 feet of a USB-enabled docking station, all data is silently uploaded in the background to the Fitbit.com website. That’s where the magic happens as it is there that the data is combined with the user’s history and eating habits and displayed as useful information that can help that user keep track of their exercise and diet regimen, and hopefully lose weight.

The devices costs $99 and because of its popularity it remains on back-order.

Couch potato inspiration
The FitBit idea started with the company CEO James Park’s fascination with the Nintendo Wii and its melding of sensors and software. “I’m a big fan of the Wii, but I was out of shape myself,” he said, “so I wanted to combine the best aspects of sensors and hardware to promote activity.”

However, the market for fitness devices is already dominated by Nike, Garmin and Polar, Omron, as well as startups such as BodyMedia (GoWearFit, $259 plus monthly subscription), Active Trainer and of course iPhone and Android apps such as RunKeeper). All of which include many of the FitBit’s capabilities, many with GPS capability. Park recognized this competition early on and after initially targeting more athletic people, he quickly revised his strategy to focus on the more sedentary—and the online user interface, which remains a strong differentiator.

This meant focusing on form factor. “We found that those that were geared toward being fit were more open to obtrusive devices,” said Park, referring to such add-ons as chest straps for accurate heart and breathing monitoring. On the contrary, those that were more sedentary wanted a less-obtrusive device—click on your belt and go. “Compared to the pedometer we’re 40 percent smaller—and wireless,” he said. “We also focused on differentiated data.”

What’s Park’s advice for designers at this stage of the development process? “Get as much validation from potential customers as possible. There are too many NRE [non-recurring engineering] costs.”
As is often the case, two of the factors that were critical to the device’s success – form factor and wireless – also proved to be the two biggest hurdles to achieving that success. The third factor, the algorithms used to process the in-coming data, is where much of the company’s intellectual property resides, but implementing those algorithms in a device measuring 2 x 0.75 x 0.3 inches proved problematic.

Compared to a tethered USB connection, wireless has clear user-experience advantages, assuming the nuances of device-to-basestation association have been worked out. However, the associated impact on design time, cost and power consumption must also be weighed carefully, said Park, particularly with such a small form factor.

“Going wireless definitely affected the mechanical design and there were layout issues given the small board and the closeness of metallic components,” said Park. “It did require a lot of adjustments to make sure it worked.”