• By
  • Timothy Hay

The recession, health-care reforms and other pressures have put the squeeze on emerging companies offering traditional medical technologies like pharmaceuticals and medical devices.

Yoshikazu Tsuno/Agence France-Presse/Getty Images
A model demonstrates the health-monitoring Fitbit Flex device, which transmits vital signs to a smartphone.

But wearable gadgets and health-tracking services–which collect data from the user, and are a major part of today’s “quantified self” trend in health care–are doing brisk business.

This week, investors from Foundry Group, Softbank Capital, True Ventures and other firms put $43 million into FitBit Inc., as reported by The Wall Street Journal blog AllThingsD. The company, which makes health-tracking wristbands and previously raised more than $20 million from investors, says its sales have been skyrocketing for years.

Also this week, Kleiner Perkins Caufield & Byers and Accel Partners invested $18 million in MyFitnessPal LLC, which tracks helps people lose weight by keeping track of calories in the food they consume relative to their exercise level.

The large dollar amounts of the deals are an encouraging sign for developers of new health technologies, where entrepreneurs often have trouble raising funding.

They also show that quantified self—or the idea that more individual health data will lead to better and less expensive treatment—is continuing to pick up steam.

Quantified self is the spawn of several of today’s top technology trends, including the popularity of smartphones, the evolution of advanced sensors, the rise of “big data” and advanced analytics and the faster and cheaper sequencing of human DNA.

People have long used gadgets—like the simple pedometer—to add important data to their fitness routines.

Today, consumers can use mobile phones, smart watches, adhesive patches, clothing with embedded sensors and a range of other accessories to track their heart rate, body temperature, blood sugar, caloric intake, sleep quality and other statistics.

And unlike a simple pedometer, the trackers of today beam data to cloud databases, where algorithms deal with massive amounts of data, combing through it in search of patterns and returning advice to consumers.

The phenomenon plays to consumers’ love for gadgets, and to the health-care system’s very real need to cut down the number of unnecessary visits to hospitals and doctors’ offices.

For this reason, players as well-known as Google Inc. have gotten into the business, using its venture division to fund 23andMe Inc., a DNA sequencing company that returns to consumers a wealth of genetic information from a simple saliva sample.

And quantified self continues to attract new entrants, like Beverly Hills, Calif.-based BioBeats Inc., which invites users to tune in to their own heartbeats, for the purpose of making music from the rhythm.

Write to Timothy Hay at timothy.hay@wsj.com