Samsung unveiled Monday its new flagship Galaxy S5 smartphone armed with a fingerprint scanner and a built-in heart rate sensor to defend its place as the worlds industry leader. Samsung made about 30 percent of all smartphones sold in the world last year, nearly twice the share of archrival Apple, which traditionally skips the annual World Mobile Congress. But Samsung, which announced its new devices on the sidelines of the February 24-27 event, is nevertheless scrambling for new revenue sources as competition in mature markets intensifies. In a struggle to stand out from the competition, including a rising challenge from China, Samsung showed off the Galaxy S5 with a light sensor on the back that gives a heart rate reading when the user touches it with his or her fingertip.