Energy limitation, heterogeneity of hardware, increase in node temperature, absence of software reusability-are major problems in existing middleware for body sensor networks. In this paper, we have proposed an event based grid middleware that solves all these problems using distributed resources. In our multi-hop communication, we have used lightweight rendezvous routing algorithm on publish/subscribe system of event based communication. To faciliate software re-use and application development, modified OSGI has been implemented in our middleware architecture. We have considered our grid middleware on a scenerio of cancer treatment with join operations of hyperthermia, chemo-therapy and radio-therapy with invivo sensors.