We have created and tested a wearable sensor network that detects a user's body position and motion as input for interactive applications. It is envisioned to take game experiences such as Dance Dance Revolution, Wii Fit, and other active play scenarios to a whole new level, augmenting or replacing the binary foot-pad and balance board with a more immersive, full-body input system. We describe the design and functionality of the sensor network to characterize and verify body pose and position, perform experiments, and report on the capabilities and limitations of such a system. Our experience shows that a distributed set of sensors around the body prevents the player from cheating the system by using motion of the device alone to trick the system. In this work we show that a relatively simple sensor network configuration can enforce proper form and ensure that the player is actively participating in the game context, while a larger configuration can be used in training applications.