The long-term vision of an Internet of Things (IoT) is approaching reality and leading hardware vendors expect shipment of 50 billion devices in the near future. Emerging Internet standards will enable this huge number of embedded machines to interconnect and cooperate---and raise the challenge of building suitable software environments that provide scalability, reliability, and security at an efficient level. In this paper, we introduce such an approach---a modified actor model and a corresponding runtime environment. In contrast to common tools, it offers a higher level of abstraction to design and program applications for constrained devices, while remaining efficient, reliable, and open to include the security extensions from the agenda of the IETF.