WatchPlant will develop a new biohybrid system technology, a wireless wearable self-powered sensor for in-situ monitoring of urban environments. This system equips urban biological organisms -plants- with Artificial Intelligence (AI) to create a smart sensor for measuring both, environmental parameters and the responding physiological state of plants, in a very early stage by the use of a barely explored fluid, phloem sap, in combination with chemical, and physical sensors. It will be integrated into complex network that allows performing distributed information processing, decision making, modeling and data fitting, paving the way for the self-awareness or self-adaptation. Additionally, it will constitute a clean energy self-powered device due to the novel use of sap, not only for transforming plants into living sensors, but also for clean energy generation. A consortium of EU research, technology centers and ambitious high-tech SMEs will stretch and combine the limits of plant physiology and bioelectronics with microtechnology, multiphysics modelling, sensor engineering, AI and environmental modelling, to transform plant into living autonomous and self-powered sensors. The project has the ambition to solve how to extract sufficient sap volume in a healthy plant, how to make long-lasting bioelectronics, and how create a smart self-powered wearable phytosensor in a single device. It also has the challenge of modelling urban environments using novel combinations of exiting parameters and explores the future role of sap in this sense. Thus, it is a promising tool to carry out weather/pollution/pandemics development forecasting systems up to social networks for proving an ecological/environmental feedback to citizens. Thus it will be possible to perform specific actions and apply efficient use of resources and correct policies, which can have a great impact not only in urban monitoring but a huge range of plant-related sectors such as agro-food industry or forestry.