A system for policy-based applications may be developed by using non-device specific policies that are executed on a policy engine. During installation, available sensor devices are identified by metadata that describes the devices within a taxonomy of sensor devices, and a separate device policy may be installed and executed by each sensor device. The policy engine, in conjunction with the sensor devices operating a device policy, may be execute a wide range of applications. In many applications, a sensor device may detect that a first policy engine is not available and send communications to a second policy engine that may be accessed through the Internet.