We present a case study in the design and subsequent use of ”OKMO”, a software program for the quantitative assessment of subjective appetite-related sensations, using a visual scale and running on a handheld computing device. OKMO runs on inexpensive Palm devices (PalmOS 4), and was built using only free and open source software technologies. Over the years it has been used in five studies involving hundreds of subjects. The aims of the present case study are: a) to expose the considerations (device availability and cost, software licensing, localization) driving the technology decisions surrounding OKMO; b) to describe the medical studies that OKMO has enabled to date; and c) to describe the experience of the researchers and research subjects who used OKMO.