The BTnode platform is a versatile and flexible platform for functional prototyping of ad hoc and sensor networks. Based on an Atmel microcontroller, a Bluetooth radio and a low-power ISM band radio it offers ample resources to implement and test a broad range of algorithms and applications ranging from pure technology studies to complete application demonstrators. Accompanying the hardware is a suite of system software, application examples and tutorials as well as support for debugging, test, deployment and validation of wireless sensor network applications. We discuss aspects of system design, development and deployment based on our experience with real wireless sensor network experiments. We further discuss our approach of a deployment-support network that tries to close the gap between current proof-of-concept experiments to sustainable real-world sensor network solutions.