The use of wireless sensor networks are vital to Precision Agriculture. Often these technologies are expensive or overly complex to producers. An open source microcontroller platform, Arduino, was used to develop a system to measure sap flow in grapevines (Vitis vinifera) in a vineyard in Greece, and to seamlessly transfer this data to a web server for storage. The performance of the system in the summer of 2014 is discussed. Management zones are a pillar of Precision Agriculture research. Spatial variability is apparent in all fields, and understanding this variability by delineating management zones can lead to better management decisions. A custom suite of applications called EZZone was developed for management zone delineation and is available for public use at ezzone.pythonanywhere.com. A demonstration and analysis of the tool is presented.