This paper presents an approach to design and deploy large-scale applications for body area networks (BANs). The approach is based on BodyCloud, which is a Cloud-based multi-tier application-level architecture. BodyCloud integrates a Cloud computing platform and the SPINE BAN middleware. It specifically provides programming abstractions, such as group, modality, workflow and view, which support the rapid and effective development of community BAN applications. This work provides an overview of the general architecture of BodyCloud and discusses several large-scale application services that can be deployed on BodyCloud.