LinkPak for

From SilverWare:

LinkPak is a collection of applications that replace the four main built-in applications. AddressLink, DateLink, MemoLink and ToDoLink appear and work exactly like their built-in counterparts except for one important feature: each of the link-enabled applications contain a Link button wherever an individual item can be selected. For instance, when viewing or editing a particular address in AddressLink, a Link button is displayed. Tapping the link button allows you to create links among the four applications. Tapping the link button for an item which has links displays a pop-up list. Selecting an item will then launch the appropriate application and display the selected entry.