We present a handheld, biomolecular detector based on a cell phone platform. This prototype integrates a conventional smart phone with a custom electrical circuit and a microfluidic chip, which enables a portable, lightweight biodetection system. An electrochemical detection scheme is utilized, allowing for rapid (<; 20 min), high sensitivity, analytical measurements. As proof of concept, Plasmodium falciparum histidine-rich protein 2 (PfHRP2) was detected in buffer solution, with a lower limit of detection of 16 ng/mL. Based on its compact size and high performance characteristics, this cell phone biodetector is highly suitable for use in remote locations for multiple applications including disease diagnosis, water quality monitoring and pathogen/toxin detection.