One of the key factors associated with mobile data services is the ability to provide greater contextualization of user activity through information such as personal presence. One of the barriers to the provision of context information for services operating over mobile phone networks has been the inflexibility of the existing architecture which has its roots in voice services. The aim of IMS is to introduce greater flexibly to the mobile phone networks for a range of data services using a new architecture based on SIP. In this paper we present the design and implementation of a novel IMS presence service called SipPres running on a mobile phone that allows users to illustrate a greater range of contextualized information. The application practically illustrates how presence can be used to enrich a range of mobile services and the tremendous opportunities IMS will offer.