Pervasive systems are todays hardware/software solution to Mark Weisers 1991 vision of Ubiquitous Computing, with the aim of enabling everyone to enjoy computer services by means of the surrounding environment. Mainly thanks to low-cost wireless communication technology, pervasive services can be now implemented easily. Local or network advanced applications can be joined everywhere, simply by means of a mobile terminal such as those (cellular, PDA, Smartphone, ...) we are already accustomed to carry with us. Pervasive systems aim to free people from conventional interaction with desktop and laptop computers and allow a new human-environment interaction to take place on the basis of wireless multimedia communication. This book has been written mainly for students of masters level and PhD courses in engineering faculties. The book discusses the fundamentals of pervasive systems theory as they are currently studied and developed in the most relevant research laboratories. The book also includes some examples of pervasive applications which were implemented by last-year students as a requirement for passing the Grids and Pervasive Systems exam. All the applications take advantage of Bluetooth technology as a free wireless communications medium and are ready to run, even if they are just laboratory products and need to be improved and customized for commercial use.