In Scientific American this month I wrote about the explosion of personal, wearable health-tracking devices. The popularity of smartphones and the availability of cheap sensors are enabling a revolution in self-monitoring and self-measuring—and we're just getting started.

You've probably heard of the fitness bands such as the UP band and the Fitbit. But wristbands are just the warm-up act. Here's what else is coming down the pike.

Spree Headband: This $300 band (also available as a baseball cap) does more than keep the sweat out of your eyes when you're running, walking, biking, weight lifting or skiing. It also monitors your heart rate, body temperature, distance, time, calories burned and speed. All this data is sent to a corresponding smartphone app. A headband makes a lot of sense but this one's pricey and, surprisingly, does not measure the number of steps you've taken.

Sensoria Fitness Socks: "Each Sensoria Fitness product is infused with textile sensors that gather heart rate, force and pressure data." And that includes socks. These may cost $150—about $145 more than most socks—but when paired with the associated Bluetooth-enabled anklet they track a runner's cadence, foot-landing habits and weight distribution. You follow the results on your phone.

Polar Cardio Sports Bra: There's a heart-rate monitor built right into this bra, which is machine-washable. "This eliminates the need for a separate heart rate monitoring chest strap. No strap. No worries. No excuses," says the Web site. Note that the bra communicates only with a Polar cardio watch—not your phone. And purchasers on Amazon note that figuring out which size to get can be tricky.

HAPIfork: Most people laugh when they see this thing. There's really such a thing as battery-powered silverware? Indeed. The HAPIfork ($100) is a Bluetooth fork whose sole job it is to make you healthier by slowing you down. It lights up and vibrates—and your phone screen goes red—if you're shoveling food into your mouth too fast. (Eating more slowly gives your brain time to tell you you're full, so you eat less.)

SexFit: These days, people are putting trackers anywhere—and that, inevitably, leads us to this "sexual fitness tracker." The gentleman wears this ring (currently only a prototype), which tracks his pace per minute and calories burned; this data is sent via Bluetooth to a phone app. At that point, you can analyze stats and, at your option, post your latest data to Facebook or Twitter.