Current technological developments have favoured the popularisation of portable electronic devices. However, the demand for advances is increasing, not only in the technical field, but also in the functional and ergonomic domain. These devices must be small and robust; and sometimes there is no room for integrated interfaces, and these must be externalised. To respond to these requirements, User-Centred Design methodologies are used, where prototyping plays a fundamental role. The prototyping of wearables requires a complicated integrated design-technology approach that facilitates the evaluation of the devices with real users, sometimes without technical expertise and in hostile environments. In this paper we discuss the use of mobile application development platforms based on block programming as a tool for designers in wearable prototyping. This stimulates a comprehensive design from the first phases of the project. This type of platform provides a visual development environment, easy to use, with predefined components, and an open community behind it which favours a fast and accessible validation of the proposed designs. To provide means for designers who want to enter the field, we present the functions that have been identified as basic in a wearable prototyping application; the elements involved; and conclusions for structuring its design and development.