Continuous wireless wide area network (WWAN) access for mobile devices in future pervasive systems may be limited by battery power and may generate extensive data telecommunication costs. In this paper, we develop a new message notification protocol (MNP) to enable mobile users to maintain a continuous presence at their instant messaging (IM) server while avoiding long, idle connections. In MNP, mobile users cooperatively share a single message notification channel to reduce users’ telecommunication charges and extend a device’s battery life. A device may turn off its WWAN interface for most of the time to save power, and only needs to contact the IM server when needed. Precise group information does not need to be maintained by a mobile device. Message notification exchanged between the IM server and the peer group is represented by a compressed Bloom filter to further reduce the protocol overhead and provide additional privacy and security. The results of performance evaluation show that the MNP protocol could be able to save significant energy consumed in a mobile device.