This paper grounds on the SAPERE project (Self-Aware PERvasive Service Ecosystems), which aims at proposing a multi-agent framework for pervasive computing, based on the idea of making each agent (service, device, human) manifest its existence in the ecosystem by a Live Semantic Annotation
(LSA), and of coordinating agent activities by a small and fixed set of so-called eco-laws, which are sort of chemical-like reactions evolving the distributed population of LSAs. System dynamics in SAPERE is complex because of openness and due to the self-* requirements imposed by the pervasive computing setting: a simulation framework is hence needed for what-if analysis prior to deployment. In this paper we present a prototype simulator which - due to the role of chemical-like character of eco-laws - is based on a variation of an existing SSA (Stochastic Simulation Algorithm), tailored to the specific features of SAPERE, including dynamicity of network topology and pattern-based application of eco-laws. The simulator is tested on a crowd steering scenario where groups are guided, through public or private displays, towards the preferential destination and by emergently circumventing crowded regions.