A communication system is provided that uses loosely-coupled client-server architectures to improve the efficiency of communications. The communication system includes client and facilitator applications. The client application is a component of processor-based mobile communication devices. The facilitator application is hosted on one or more servers or other processor-based devices, and communicates with the client application via one or more couplings. The facilitator application can also be distributed among one or more portable processor-based devices including the communication devices hosting the client application. The communication system improves efficiency of voice communications by allowing communication device users to dynamically manage how and when mobile calls take place, intelligently screen calls based on caller identity, urgency, and subject matter, determine which contacts in a directory are available to talk and which ones choose not to be disturbed, and increase accessibility of enterprise and personal contact information from mobile phones.