Engineering distributed applications and services in emerging and open computing scenarios like the Internet of Things, cyber-physical systems and pervasive computing, calls for identifying proper abstractions to smoothly capture collective behaviour, adaptivity, and dynamic injection and execution of concurrent distributed activities. Accordingly, we introduce a notion of “aggregate process” as a concurrent field computation whose execution and interactions are sustained by a dynamic team of devices, and whose spatial region can opportunistically vary over time. We formalise this notion by extending the Field Calculus with a new primitive construct, spawn, used to instantiate a set of field computations and regulate key aspects of their life-cycle. By virtue of an open-source implementation in the ScaFi framework, we show basic programming examples and benefits via two case studies of mobile ad-hoc networks and drone swarm scenarios, evaluated by simulation.