This work addresses the creation of a development framework where application developers can create, in a natural way, immersive physical activities where users experience a 3D first-person perception of full body control. The proposed framework is based on commercial motion sensors and a Head-Mounted Display (HMD), and a uses Unity 3D as a unifying environment where user pose, virtual scene and immersive visualization functions are coordinated. Our proposal is exemplified by the development of a toy application showing its practical use.