Rapid, on-site, accurate and wireless measurement of small, hazardous molecules and biomarkers is one of the biggest challenges in nanobiotechnology. Herein, we devised a new and a smartphone-based Portable and Wireless Diagnostic System (PAWS) for on-site, quantitative, and rapid analysis of various analytes in real samples. As a proof of concept, we employed gold nanoparticles (GNP) and an enzyme, horse radish peroxidase (HRP) to generate colorimetric signal in response to the target molecules (melamine and hydrogen peroxide) where the colorimetric signal is converted to the electronic signal by inbuilt electronic circuit of the device. Then, the converted electronical signal is transmitted via wireless multimeter to smartphone which processes the data and displays the results including the unknown concentration of analytes and its significance. This handheld device has a great potential as a programmable and a simple platform for on-site detection of various analytes within 20~30 minutes depending on the analyte.