In this paper we present a novel approach to fault-tolerant group membership for use predominantly in collaborative computing environments. As an exemplar, we use the Collaborative Computing Transport Layer which offers reliable atomic multicast capabilities for use in collaborative environments such as the Collaborative Computing Frameworks (CCF). Specific design goals of the approach are the elimination of processing overhead due to heartbeats, support for partial failures and extensibility. These goals are satisfied in an approach which uses an IP multicast failure detector and two election based algorithms. By basing failure detection on IP multicast, the need for explicit keep-alive packets is removed, thus in the absence of failures the approach imposes no overhead.