System on Devices (SyD) is a specification for a middleware to enable heterogeneous collections of information, databases, or devices (such as hand-held devices) to collaborate with each other. This paper illustrates the advantages of SyD by describing a prototype calendar of meetings application. This application highlights some of the technical merits of SyD by exploiting the use of coordination links. Based on the underlying event-and-trigger mechanism, these links allow automatic updates as well as real-time enforcements of global constraints and interdependencies, not available with existing calendar applications. Additionally, the calendar application illustrates coordination among heterogeneous devices and databases, formation and maintenance of dynamic groups, mobility support through proxies, and performance group transactions across independent data stores.