The increasing pervasiveness of wearable sensors opens new scenarios in the continuous monitoring of health parameters. In particular, wearables are becoming the sensing part of the Internet of Medical Things (IoMT), i.e. IoT in the healthcare field. Currently, several IoMT based devices capable of measuring blood pressure (BP) are starting to be offered on the market, giving the possibility to monitor BP every time and everywhere. An open issue is the lack of the traceability and reliability of the BP measurements. The aim of this paper is stimulating the research to fulfil this lack by presenting an overview for IoMT and commercial wearables in BP monitoring, from a metrological point of view.