From Forum Nokia Wiki

The LocalApp scheme is one generic scheme for local application launching that could also be used to launch the Messaging application, Calendar, and Contacts. For launching the applications or clients, every app-header(URL scheme) must be case sensitive.

<a href="localapp:calendar">open calendar</a><br/>
 
<a href="localapp:contacts">open contacts</a><br/>
 
<a href="localapp:messaging">open messaging</a><br/>