SAN FRANCISCO Google on Thursday unveiled an upgraded fitness app which uses smartphone camera capabilities to measure respiration and heart rate. Google Fit already uses smartphone sensors to figure out how far people walk or how many calories they have burned, but new features rolling out to Google Pixel phones will add pulse and breathing to health data crunched by the app. Sensors and software that make it possible to take stunning photos with smartphones or automatically adapt streaming video to how handsets are held can be used to sense respiration and heartbeat, according to Google health technologies team leader Shwetak Patel.