The availability of free Software Development Kits for recent mobile device platforms challenges many developers in realizing applications for the growing Smartphone market. In many cases such applications may interoperate in their working environment using mechanisms similar to the inter-process communication (IPC) and made available by the mobile operating system. Unfortunately, mobile devices lack in flexible solutions for making these communications secure. In this paper we propose a framework to secure the message exchange with the services installed on Google Android mobile devices. VASs realized by different providers are discovered, used and composed by an Application Frame designed for realizing complex goals. We implemented a prototype of our proposed framework on a real device and we performed extensive testing to measure the overhead introduced by the cryptographic operations required to protect the inter process communication.