Fitness trackers have become a popular piece of consumer electronic equipment, with a range of models from a variety of manufacturers. Many of these commercial offerings, however, leave the consumer with the prospect of their data being drawn off to a cloud server and sold to the highest bidder, trading convenience for a loss of privacy. If only there were a fitness tracker offering complete control!

The OpenHAK is an open-source fitness tracker in a 3D printed wristwatch case that measures your heart rate and counts your steps, offering the resultant data for you to collect via Bluetooth. At its heart is a Sparkfun Simblee module, with heart rate sensing through a Maxim MAX30101 and step counting .by a Bocsh BMI160. It’s designed for expandability from the start with a header bringing out useful interface lines. In the prototype, they’ve used this to support a small OLED display. The result is a fitness tracker watch that may not match some of the well-known proprietary devices, but which remains completely open and probably costs a lot less too.

We’ve seen quite a few fitness tracker apps over the years, including a conversion to an EEG, and custom firmware for some commercial trackers.