A wearable low-power hybrid vision-inertial tracker has been demonstrated based on a flexible sensor fusion core architecture, which allows easy reconfiguration by plugging-in different kinds of sensors. A particular prototype implementation consists of one inertial measurement unit and one out-ward-looking wide-angle smart camera, with a built-in DSP to run all required image-processing tasks. The smart camera operates on newly designed 2D bar-coded fiducials printed on a standard black-and-white printer. The fiducial design allows having thousands of different codes, thus enabling uninterrupted tracking throughout a large building or even a campus at very reasonable cost. The system operates in various real-world lighting conditions without user intervention due to homomorphic image processing algorithms for extracting fiducials in the presence of very non-uniform lighting.