Fitbit Prototyping
While many think of Arduino as strictly for hobbyists, its ease of use makes it a great tool for prototyping products for the mass market. The designers of the Fitbit, a device for tracking your level of activity throughout the day, wrote to the Arduino team to tell them that they’ve been doing just that:

We had a nice note from Shelten Yuen to say “We’ve been using Arduino for rapid prototyping for a few years now. It’s been a great tool for us in trying things out quickly.” It’s always nice to hear how people use Arduino at work as well as in their hobbies.