WITH Christmas coming, the geeky fitness enthusiast, dieter or insomniac might think of asking Santa for a self-monitoring device. These gadgets — wearable sensors and mobile apps that count and analyse a range of indicators, such as daily steps, heart beats or sleep patterns — are changing the way users behave. It’s estimated that in a few years’ time there will be around 170 million wireless devices tracking personal health around the world. They could, some say, help make us all healthier by providing a new pool of data for scientists to analyse. Self-tracking isn’t new — athletes and people with chronic conditions such as migraines, diabetes and allergies have used it in the past to shed light on fitness levels, impending danger or what triggers symptoms. But in the last few years new consumer products have come on the market that make monitoring easier and more precise. They generate a large amount of data that can be analysed and shared using social media, which adds a social dimension to otherwise lonely endeavours like trying to lose weight or getting fit. Using wireless transreceivers, many of these devices can transmit data to your cellphone or computer. One such device is Fitbit, which measures steps, calories and sleep patterns (see accompanying story). Zeo records a more detailed picture of sleep cycles, while Zephyr tracks heart rate, motion and respiration. All are available in South Africa and Nikki Friedman, brand manager for Fitbit in South Africa, said the product has been “really popular” here, and was sold out within the first five days of its launch. Cape Town even has a local chapter of Quantified Self, an overseas website that describes itself as “an international collaboration of users and makers of self-tracking tools”. While much of the data produced is of no interest to anyone but the user, experts say one consequence of the self tracking movement is that shared data could help produce new medical insights. Another is more people seeking early help for symptoms detected through patterns picked up in self-monitoring.