Out-patient medication administration has been identified as the most error-prone procedure in modern healthcare. Under or over doses due to erratic in-takes, drug-drug or drug-food interactions caused by un-reconciled prescriptions and the absence of in-take enforcement and monitoring mechanisms have caused medication errors to become the common cases of all medical errors. Most medication administration errors were made when patients bought different prescribed and over-the-counter medicines from several drug stores and use them at home without little or no guidance. Elderly or chronically ill patients are particularly susceptible to these mistakes. In this paper, we introduce Wedjat, a smart phone application designed to help patients avoiding these mistakes. Wedjat can remind its users to take the correct medicines on time and record the in-take schedules for later review by healthcare professionals. Wedjat has two distinguished features: (1) it can alert the patients about potential drug-drug/drug-food interactions and plan a proper in-take schedule to avoid these interactions; (2) it can revise the in-take schedule automatically when a dose was missed. In both cases, the software always tries to produce the simplest schedule with least number of intakes. Wedjat is equipped with user friendly interfaces to help its users to recognize the proper medicines and obtain the correct instructions of taking these drugs. It can maintain the medicine in-take records on board, synchronize them with a database on a host machine or upload them onto a Personal Heath Record (PHR) system. A proof-of-concept prototype of Wedjat has been implemented on Window Mobile platform and will be migrated onto Android for Google Phones. This paper introduces the system concept and design principles of Wedjat with emphasis on its medication scheduling algorithms and the modular implementation of mobile computing application.