1. A method for determining pulse transit time using a handheld device, the method comprising: generating an electrocardiogram (EKG) for a user of the handheld device, wherein the EKG is generated from two conductive contact points on the handheld device in contact with two portions of the user's body; de-noising the EKG to identify a start time when a blood pulse leaves a heart of the user; receiving a plurality of video images of the user; de-noising the plurality of video images of the user to identify a pressure wave indicating an arterial site and a time when the pressure wave appears; and determining a pulse transit time (PTT) based on the de-noised EKG and the de-noised video images.