Disclosed is an integrated handheld computer and telephony system. Integration of the handheld computer and telephony system is at the physical and operational level. For example, the integrated handheld computer and telephony system physically integrates a handheld computer with a mobile (e.g., cellular) telephone. In addition, the handheld computer is distinct from telephony system in that they are logically separable. However, they are also operationally integrated, for example, the telephony system executes a telephone application on the processor of the handheld computer. Likewise, the handheld computer can execute applications, for example, a phone book, that can be used to launch the telephony application.