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Beyond the Pedometer

A two-part kit lets some Nike shoes talk to Apple iPods. Will it spur a range of consumer applications for wireless sensors?
July 28, 2006

Nike and Apple Computer recently unveiled a joint product: the Nike+iPod Sport Kit, which uses a wireless sensor to monitor pace, distance, time, and calories burned while walking or running. Some experts believe the Sport Kit is the forerunner to wireless, personal sensors with myriad functions, from tracking locations to monitoring biometrics.

This kit features a wireless sensor in the insole that gathers data about your workout and sends it to an iPod. (Credit: Wade Roush)

The Sport Kit turns iPod Nanos and specialized Nike shoes into a feedback system that continuously measures workout activity and updates a user’s progress. The kit contains just two pieces: a receiver that attaches to an iPod Nano (it’s not compatible with other iPods) and a thumb-sized sensor that slips into a slot under the insole. The sensor monitors physical activity and transmits the data wirelessly to the receiver, which then sends it to the iPod, where it’s stored.

The data is wirelessly sent over the same radio frequency used for Wi-Fi and Bluetooth (2.4 gigahertz), using a proprietary wireless technology. It’s powered by a battery that Apple says has a lifetime of 1,000 hours – long enough to outlast the running shoe if the sensor is put in sleep mode when not in use.

Other technical details of the sensor are unclear; Apple declined to answer such questions. But according to John Huggins, executive director at the Berkeley Sensor & Actuator Center at the University of California at Berkeley, the sensor most likely contains a simple accelerometer, similar to those used to deploy airbags in cars, that measures the acceleration of a foot during running or walking. It could also contain, he says, a small amount of memory, logic circuitry, and a transceiver that sends and receives wireless signals.

Gadgets that give workout feedback aren’t new, of course. Walkers, joggers, and runners have long been using pedometers to count their steps and wrist watches that monitor their heart rates. The kit goes a step further, though, by hooking up with the iPod, already a popular consumer product. In addition, the data from it can be uploaded to a website (, so users can monitor their progress and set new fitness goals. In this way, the gadget provides a platformto keep track of workouts.

But the sensor is disposable and needs to be replaced when the battery wears out. In future versions, batteries could be avoided all together, says Berkeley’s Huggins, since researchers have shown that power-harvesting circuits that store energy from vibrations can be used instead of batteries in some sensor applications, and the environment of a running shoe could be ideal for such technology. If this modification were made, it could give the sensor “an extended or infinite life,” he says.

To Huggins, the kit is exciting because it’s a “clever and cute” application for wireless sensors, and opens up opportunities for added features and new applications. For instance, he says, if the sensor used a more complicated accelerometer – one that could measure acceleration in multiple directions – it would be possible to calculate calories burned on inclines and stairs. Also, it could calculate the shock experienced when a foot hits the ground. As shoes wear out and shock increases, you could be reminded that it’s time to buy new shoes.

What’s more, adding GPS capability to the system could let people map their jogging routes. This improvement, Huggins says, could be done easily and inexpensively. Rather than installing a GPS receiver into the sensor, it could be “part of the higher valued iPod, which could re-use the GPS for other location-based services,” he says. While out for a morning jog, your iPod could help find a coffee shop or a bus route, if you get tired.

Real-time biometric data could also be integrated with such a sensing device. Pulse, temperature, glucose, and lactate levels could be monitored with an array of microneedles, says Huggins. And it wouldn’t have to be messy or painful, he says, because microneedles can be as short as 150 micrometers. At that size, Huggins says, the needles would penetrate the skin without touching nerves or blood vessels.

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