A sensor worn on the wrist could improve how blood pressure is measured, say researchers.
Normally blood pressure is measured in the arteries in the arm, but the pressure at the heart might be a better predictor of future health problems.
If blood pressure is too high it can lead to heart attacks and stroke.
About a third of people in the UK have hypertension, dangerously high blood pressure, but most are unaware of the condition.
A team at the NHS National Institute of Health Research (NIHR) trialled the sensor, which contains a mini-plunger that moves up and down as blood pulses past with every heartbeat, the BBC reported.
A computer programme in the wrist strap used this "pulse wave" to work out the pressure in the heart.
This was compared with measures taken from sensors in patients' hearts.
According to Prof Bryan Williams, the director of the NIHR University College London Hospitals Biomedical Research Centre, it was remarkably accurate.
The study is published in the journal Hypertension.