A Toronto researcher is developing a smartphone app that he says can monitor blood pressure by analyzing a short selfie video. Kang Lee’s technology takes readings by tracking blood flow patterns in the face. Researchers asked over 1,300 participants in Canada and China to take two-minute videos of their faces on an iPhone using the app and compared the readings to those from a traditional cuff-based blood pressure monitor.The smartphone blood pressure measurements were about 95 per cent accurate.