Many mountain bikers already use smartphone apps to track basic ride metrics such as route/distance travelled, elevation gain, and speed. A group of four Danish cyclists wanted to take things significantly further, however, so they created TrailSense.

Currently the subject of a Kickstarter campaign, the TrailSense system consists of a water/shock-resistant sensor and a subscription-based app.

Zip-tied onto the bike's non-drive-side chainstay, the sensor measures speed via a wheel-mounted magnet. The device also contains a barometer that tracks elevation gain, plus it's equipped with a 9-axis inertial measurement unit (IMU) – the latter is an accelerometer/gyroscope combo, and it tracks the bike's movement up to 100 times per second.

Data is continuously transmitted by Bluetooth Low Energy to the app, on the rider's smartphone. That app accesses the phone's GPS to track the bike's location. Once the ride is over, the cyclist is able to review not only the usual route, distance, average speed and elevation info, but also metrics such as the airtime and length of jumps, impact upon landing, and cornering speed.

Additionally, the app provides a rating of the rider's line choice for a given stretch of trail, which is based on their stability and jump-landing impact as compared to that of other TrailSense users on the same trail. It also rates the difficulty of the trail, plus it can compare the user's performance to the predicted performance of a pro rider on that same trail, or to that of other TrailSense users via an online leaderboard.

Finally, if the sensor detects that a crash has occurred, it triggers the app to send an emergency notification to a predetermined list of contacts (unless the rider stops it from doing so first). This is similar to what is offered by the ICEdot sensor, the technology of which has now been integrated into the Specialized ANGi line of helmets.

Battery life for the sensor sits at a claimed 20 hours per USB-charge. The app is presently iOS-only, although an Android version is in the works.

Should you be interested, a pledge of DKK 800 (about US$121) will get you a TrailSense sensor and a 12-month app subscription. Assuming it reaches production, the sensor ought to sell for about $140, with a one-year subscription going for around $37. Riders who are interested mainly in tracking their jumps might also want to check out the successfully-crowdfunded ShredMate.

The TrailSense system is demonstrated in the following video.

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