Mobility challenges and independent travel are major concerns for blind and visually impaired pedestrians. Navigation and wayfinding in unfamiliar indoor environments are particularly challenging because blind pedestrians do not have ready access to building maps, signs and other orienting devices. The development of assistive technologies to aid wayfinding is hampered by the lack of a reliable and cost-efficient methods for providing location information in indoor environments. Here we describe the design and implementation of a digital sign system based on low-cost passive retro-reflective tags printed with specially designed patterns that can be readily detected and identified by a handheld camera and machine-vision system. Performance of the prototype showed the tag detection/recognition system could cope with the real-world environment of a typical building.