The development of portable sensors for rapid, on-site and cost-effective detection of a broad range of targets has long been sought, because such sensors have the potential to revo-
lutionize scientific research, environmental monitoring and per- sonal healthcare in urban areas in developed countries as well as rural areas in developing countries1–10. Despite their great promise and many years of investigation, only a limited number of sensors are commercially available to the public at present. Perhaps the most successful example of such a sensor is the personal glucose meter (PGM)11,12, which is widely available in stores and has either saved or improved the quality of lives of millions of diabetic patients worldwide. However, it can only detect a single target, blood glucose. In this Article, we report a novel methodology that uses a commercially available PGM, but link it with functional DNA sensors to detect and quantify a broad range of non-glucose targets involved in diagnosis and environmental monitoring. These targets range from recreational drugs such as cocaine to important biological cofactors such as adenosine, as well as disease markers (for example, interferon-g for tuberculosis) and toxic metal ions (for example, uranium).