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 outward-looking wide-angle Smart Camera, with a built-in DSP to run all required image-processing tasks. The Smart Camera operates on newly designed 2-D 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 any user intervention due to homomorphic image processing algorithms for extracting fiducials in the presence of very non-uniform lighting.