A fuzzy just-in-time (JIT) ubiquitous service networked system is established in this study. This system is an innovative application of mobile commerce, ubiquitous computing, and ambient intelligence. The intended user is a traveler who must decide on the best service location along the planned route; the system arranges the service when the user demands it, so that when the user arrives at the service location the required service is ready. This system applies the "just-in-time" concept to mobile commerce, ubiquitous computing, and ambient intelligence. This innovation has great potential for providing better services in these fields. The issue of how to determine the JIT service location and path in a ubiquitous service network is critical; however, because data about the user's position is inaccurate, the task is difficult. To tackle this difficulty, a FINLP model is formulated, and a fuzzy version of Dijkstra's algorithm is proposed. A test system has been established to evaluate the feasibility of the proposed methodology. Based on the experimental results, the proposed JIT ubiquitous service networked system was able to reduce the user's average waiting time by 74%.