The development of low-cost diagnostic tools is essential for translation into various clinical and low-resource settings. Current advances in solid-state lighting, smart-phone capabilities, and 3D printing provide an ideal environment for the development of low-cost imagers for point-of-care diagnostic applications. Protoporphyrin IX (PpIX) based photodynamic therapy (PDT) for actinic keratosis (AK) and non-melanoma skin cancers (NMSC) is widespread, yet no diagnostic point-of-care tools are commonly used to account for the heterogeneity of PpIX accumulation between patients and between lesions. These heterogeneities are correlated with treatment outcomes, such that PpIX dosimetry can provide guidance in PDT and can be used to direct critical decisions about treatment time, retreatment, or further skin preparation. Here, we report on a low-cost smart-phone based dosimetry system designed for use in individualized PDT treatment planning. This hand-held dosimetry system uses an iPhone 6s smartphone alongside a custom app for streamlined image capture and analysis, custom LED board and electronics for PpIX excitation, and a 3D printed base for system integration and measurement standardization. The system has been tested on mice incubated with Ameluz for 10-400 minutes, imaging every 10 minutes. The images showed monotonic response over time with saturation occurring around 3hrs. Linearity of PpIX vs. measured fluorescence was confirmed with 1% intralipid phantom imaging, with a lowest detectable level of 0.05 μM and highest non-saturated level of 4 μM. With the data to date confirming the viability of the system to measure the production of PpIX relevant for skin PDT, preparations for human clinical imaging are underway.