Blood pressure has been measured with a cuff for over a 100 years. Recently, various devices and smart phone applications that measure blood pressure without a cuff using pulse transit time (PTT) have become available. These measurements are based on the inverse relationship between blood pressure and PTT. PTT constitutes the time delay between the QRS complex on ECG and the onset of a photoplethysmography pulse wave, for example in the finger. Since these measurements are relatively more user-friendly than conventional cuff-based measurements, they may aid in more frequent blood pressure monitoring by patients themselves. Initial validation studies, however, seem to suggest that blood pressure measurement using PTT is not accurate. Given the current pace of development in PTT-based blood pressure monitors it seems likely that physicians will be increasingly confronted with measurements from these devices. For the time being, it seems wise to not recommend these types of monitors to patients and to avoid using any of their measurements when making diagnostic or therapeutic decisions.