Japanese firms are jumping into the race to manufacture a new generation of wearable devices that will link people more intimately with the Internet as they grow more dependent on gadgets to manage their lives.

NTT Corp. and Toray Industries Inc. will soon release shirts that can monitor people's heart rates and take electrocardiograms, while Sony Corp. will push "life-logging" wristbands that digitally record and store data on their daily activities. Smaller firms and startups are also entering the fray.

Manufacturers say they believe the market for wearable devices, jolted by Google Inc.'s privacy-threatening Google Glass spectacles, will grow into a big one amid reports that Apple Inc. is plotting its foray into the market.