Via peer-to-peer sharing, we envision highly mobile users cooperating by sharing telecommunication connections to support a continuous messaging notification channel. Peer-to-peer sharing would enable a reduction of users' telecommunication charges and devices' battery consumption. Nevertheless, without a centralized trust authority, people lack the incentive to cooperate with a group of strangers. We present a new distributed trust framework and a credit system to solve this problem. Trust is evaluated based on a user's own experience and information obtained from others. The credit system is built on top of the trust system to ensure that each user appropriately takes turns providing the proxy service for the group of peers. No centralized authority or long-term accountability is needed. Simulation results demonstrate that this framework is stable and efficient. Fairness is maintained among users and each user may benefit in proportion to its contribution to the group.