The common desire to be connected "anytime, anywhere, anyway, and to anything" leads to explosive growth of mobile computing and speedy emergence of new wireless technologies, applications, and devices in recent years. In this array of heterogeneous systems, intelligent handover (HO) decision, beyond traditional ones that are based on only signal strength, is needed so that terminals can select the best option available from diverse networks and services as per user requirements. In the process, it would enable user applications to switch automatically between active interfaces that best suit them based on application requirements and interface capabilities, and to use multiple radio interfaces simultaneously. To fulfill the above requirements, this paper describes the architecture of a context-aware vertical HO decision model suitable for multimode mobile devices in heterogeneous networks and evaluates its performance for vertical HO between GPRS and WiFi.