A developer and Frisbee fan turned AirPods into a flying-disc stat tracker, using motion sensors to measure throws in a clever demonstration of what Apple's earbuds can do beyond playing audio.

Sharhan demonstrated Kinapod Disc on Reddit on July 20. The setup requires users to make a small hole in the center of a flying disc and insert one AirPod stem-first.

Once it's mounted, the AirPod sends motion data to an iPhone while Kinapod Disc detects each throw and records spin rate, total revolutions, estimated release speed, and airborne time.

It's a fun albeit expensive solution to the problem of throwing a plastic disc without enough statistics. It's also a clever use of motion sensors Apple builds into AirPods.

As of July 23, Kinapod Disc is available in early access through Apple's TestFlight. It hasn't been released through the public App Store, and Kinapod hasn't announced its eventual price.

Kinapod Disc turns AirPods motion data into throw statistics

Kinapod Disc receives motion data from the AirPod while the disc is in flight. The iPhone app uses the information to recognize individual throws, store practice sessions, and create charts showing the results.

Spin rate comes directly from the AirPod's gyroscope, according to Kinapod, while the app calculates how many revolutions the disc completes. Release speed and airborne time are estimates derived from the motion data rather than certified measurements.

Kinapod's estimated release speed and airborne time make the app more useful for comparing throws over time than determining whether a backyard toss reached professional Frisbee speed.

Users can leave the second AirPod in an ear and have the app announce statistics after each throw. Kinapod Disc can also call out session and personal records, create shareable summaries, and export sessions to Strava.

Sharhan said the app can add heart-rate information from compatible AirPods or an external Bluetooth heart-rate monitor. Heart-rate data is optional and doesn't affect the motion measurements collected by the AirPod attached to the disc.

Apple built the sensors for something slightly less adventurous

The experiment works because Apple's Core Motion framework gives developers access to motion information from supported headphones. Apple's CMHeadphoneMotionManager lets apps work with orientation, acceleration, and rotation data.

Apple uses headphone movement for features such as Spatial Audio and dynamic head tracking. Developers can tap into the same capabilities for interactive audio, games, exercise tracking, and other experiences built around movement, as Apple explained during a WWDC 2023 session about AirPods motion data.

Kinapod Disc applies that technology while someone hurls an AirPod across a field.

Young man outdoors holds a white disc with a small sensor attached, beside a smartphone screen showing a disc practice tracking app with speed, spin, and throw statisticsShowing off the AirPod disc. Image credit: Disastrous-Body-297

The AirPod has to sit in the exact center of the flying disc. Kinapod says that position lets the disc rotate around the sensor while limiting imbalance and improving the app's calculations.

Sharhan said an AirPod weighs less than 5 grams and that he couldn't feel a meaningful difference while throwing. He also said the friction-fit mount stayed secure because the stem isn't completely cylindrical.

On July 23, Sharhan said the AirPod had shown no problems after hundreds of throws, although he acknowledged that several months of use would be needed to judge its durability. However, repeatedly throwing an AirPod is experimental rather than an Apple-recommended use.

The flying disc needs permanent modification

Kinapod instructs users to make a hole roughly the width of an AirPod stem using a drill, heated tool, or hole punch. The AirPod is then inserted stem-first until it sits flush with the disc and stays in place through friction.

Users also have to disable Automatic Ear Detection in the AirPods Bluetooth settings. Otherwise, the AirPod can stop sending motion data after deciding it's no longer inside an ear.

Kinapod recommends briefly playing audio when the app is waiting for motion because that can wake the data stream. It also tells users to select the AirPod mounted in the disc as the active microphone.

Drilling into a flying disc and repeatedly throwing an expensive earbud won't appeal to everyone.

Kinapod Disc nevertheless shows what developers can build by repurposing sensors that millions of people already carry. It's absurd, over-engineered, and very cool, which may make it the most compelling AirPods accessory yet.