Rich Internet Applications provide, in conjunction with Internet push technologies, a powerful framework to bring use cases formerly reserved to server applications to the client, and to ease their use. In this paper we present a novel approach of monitoring and processing event streams directly in the browser. Our proposed general-purpose framework aims at the design of event-driven, reactive and adaptive Rich Internet Applications. We propose to interweave complex event processing with declarative rule execution directly on the client-side. Our work is based on a novel eventcondition-action rule language tailored to the needs of Rich Internet Applications as well as algorithms capable of detecting complex events and executing rules. The whole approach will be illustrated by means of an example originating from the field of algorithmic stock trading.