BARCELONA, Spain — Samsung on Monday unveiled a new smartphone with a built-in heart rate monitor to complement three upcoming fitness devices, as the Korean company tries to turn its technological wizardry into lifestyle products that matter.

The new Galaxy S5 phone has a slightly larger screen than its predecessor, at 5.1 inches diagonally instead of 5 inches in the S4. But the size increases have slowed down compared with previous jumps.

Rather, Samsung is focusing on other parts of the phone. The screen itself adapts to changing external conditions and gives you an option to dim it when you don’t want to disturb others near you.

The phone has a 16 megapixel camera, sharper than the 13 megapixels in its predecessor. It promises faster auto focus. The device itself is also water resistant.

“Our consumers do not want eye-popping technology or the most complex technology,” said J.K. Shin, Samsung’s head of information technology and the mobile communications division. “They want durable design and performance.”

Samsung Electronics Co. is also unveiling a fitness band, Gear Fit, to complement two new computerized watches announced Sunday.

Samsung, the world’s largest smartphone maker, made the latest announcement during the Mobile World Congress in Barcelona, Spain.

Samsung’s Galaxy S series has emerged as one of the strongest challengers to Apple’s iPhones and has helped the Korean company surpass Apple as the world’s largest smartphone maker. According to Gartner, Samsung’s smartphones had a worldwide market share of 31 percent last year, compared with 16 percent for Apple’s iPhones.

One of the main appeals is the phone’s screen size. It has steadily increased since the 4 inches on the original S from 2010. The iPhone’s screen has stayed at 4 inches since 2012. Colors on Samsung screens also appear richer because it uses organic light-emitting diodes, rather than a standard LCD found elsewhere.