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The results of research into Surface Acoustic Wave - SAW - devices have been recognized for their efficiency and versatility in the electrical signals processing. Actual progress in the industrial application of piezoelectric materials such as Lithium Niobate (LiNbO3), Langasite (LGS), Lanthanum-Gallium Silicate La3Ga5SiO14 and Gallium Orthophosphate (GaPO4), allows the manufacturing of devices with performances, which overcome the limits obtained with quartz crystals. One of the most important applications of SAW microdevices is passively, wirelessly interrogating systems. Today, GaPO4 with its properties is by far the best suited piezoelectric material to be used in sensor applications for machine monitoring and pressure measurements, at high temperatures. SAW microdevices based on GaPO4 operate at temperatures of up to 800degC. In this paper is presented a short introduction regarding the actual level of SAW microdevices development. We discuss our investigations as a comparative study of GaPO4, Langasite, and LiNbO3, regarding their properties. Each has unique strengths and weaknesses giving advantages in different applications. Conclusions regarding trends in the development of SAW sensor devices with novel materials are presented in the end of the work.