sportswear and new smart clothing making its debut at this year's U.S. Open, shirs that track heart rate, calories burned and even stress levels. ABC's Linzie Janis checked it out. Reporter: Had it... See More
sportswear and new smart clothing making its debut at this year's U.S. Open, shirs that track heart rate, calories burned and even stress levels. ABC's Linzie Janis checked it out. Reporter: Had it comes to fashion at this year's U.S. Open, don't look at the players. Check out the ball boys. Their tight black tops might just be the technologically advanced t-shirts on the planet. Designed to make you live healthier more informed lives. Reporter: Capable of tracking heart rate, calories burned, your breathing and stress levels, even coaching you through your workout. Your breathe something shallow. Breathe deeper. Reporter: The polo tech shirt by Ralph Lauren packed with high-tech sensors embedded in the fabric. No need for wristbands or clunky heartrate monitors. This is the only hardware on the shirt. That's it. Nothing else, no other wires here. Reporter: State of the art. Yes. Hard-working ball boys like Eric testing the tees expected to hit stores next year. Let's see how fast I can get Eric's heart rate up. ? giving this guy a workout. All right. Well done. How do you feel? I feel great. You're sweating. Yes, a lot. Do you think you'll be a lot more fit at the end of this tournament. I sure hope so. Reporter: Polo and other sportswear and tech companies trying to cash in on a wearable technology craze that already has hundreds of thousands of Americans monitoring their activity on fitness wristbands. It's not just small tech companies talking about this anymore. It's, you know, a giant apparel brand. Reporter: But for all that tech, it's the simple things that keep this ball boy happy. Can I test to see if your shirt is still dry? Yes. Reporter: And it is. For "Good morning America," Linzie Janis, ABC news, new York.
This transcript has been automatically generated and may not be 100% accurate.