Fitness and lifestyle trackers are all the rage, and there are many to choose from, including the Fitbit, the Nike Fuelband, the Adidas Fit Smart, the Samsung Gear Fit, the Misfit Shine and the Jawbone Up, among many others. They do things like track your workout time, steps (like a pedometer), distance and calories burned, as well as measure your heart rate and monitor your sleep patterns. Some work in conjunction with apps on your smartphone or an online portal where you can track your data, set your goals and possibly do things like log dietary information.
The devices and apps can use the gathered data to cue you to increase or decrease your workout intensity, let you share data with other users for accountability and motivation and, in the cast of at least one company (GOQii), get you in touch with an experienced fitness coach who monitors your data, sends advice and responds to questions (for a recurring fee).
Some of these devices are worn on your wrist or ankles, some wrap around your chest and others clip onto your clothing. They may have small screens, LED status lights or no display at all. Some require plugging in to upload your data and some sync wirelessly and automatically. Some work with only one operating system while others work with several.
Many modern smartphones even have sensors now that allow phone apps to perform some of these functions, like tracking your routes or your steps. Some even have heart rate checking capabilities.
These or similar innovations could disrupt personal training and other fitness related jobs, although there are some things a wearable device or app are not going to be able to do, like make sure you're using good form -- at least for now.