Fitness trackers like Fitbit and Fuelband are great at logging how much your body moves over a given day, but if you want more detail, like the angle of your knee or the jut of your hip, you're going to need more than just one sensor. That's where Notch comes in.

The new system takes a modular approach to motion tracking. Each sensor collects accelerometer data, with up to 10 sensors funneling it all back to the user's phone at any given time. It's enough data to allow for skeletal tracking and much deeper analysis of how you're body's moving. For walking, that's simple enough — but for more complex movements like a tennis serve or a karate kick, the device offers a data-driven window into the mechanics of the body that most people have never even considered.

"Symbolic muscle memory"

CEO and co-founder Stepan Boltalin calls it "symbolic muscle memory," a way of quantifying the motion of the body in a way that most athletes only know by feel. "Martial artists want to know the height of the kick, the amplitude, all of that," Boltalin says. He's also seen interest from dancers and skydivers, who would use the device to nail down the motions of a given routine. With data from Notch, a director could quantify exactly what's out of place in a given run-through. Each sensor also has a tiny vibration motor, enabling haptic feedback to let a dancer know when they've strayed too far from the pre-programed routine.

At the moment, all we've got is hardware, but Boltalin is hoping Notch's open API will inspire custom software for dancers, athletes, and other applications he hasn't even thought of. The device will arrive on Kickstarter with three sister projects on January 28th, giving developers and early adopters their first chance at demo units after a false start this November, which saw Boltalin abruptly pulling Notch from the platform after deciding it wasn't ready. Unlike earlier indie hardware startups that relied on Kickstarter to pay for prototyping, Boltalin says he wanted a working model before he asked backers to pitch in.