evidence: If you have high blood pressure, home monitors can be a great way to track your levels and keep them under control. Most of the devices currently available are versions of what your healthcare provider uses: stand-alone devices with cuffs that you apply to your wrist or upper arm. [...] Smartwatches, fitness trackers, and other devices that aim to measure your blood pressure without an inflated cuff, however, do things differently. They gather other biological data from your body and use that to approximate your blood pressure. A number of devices do this by using optical sensors to detect the movement of blood inside your body. A common metric that can be used to estimate blood pressure, called pulse transit time, represents how long it takes a pressure wave created by a heartbeat to travel between two points along an artery. [...] A few smartwatches purport to measure blood pressure in the standard way, using an inflatable cuff.