Nowadays, smart mobile devices such as tablets and accompanying applications (apps) are a part of young children's daily lives. In kindergarten education, properly designed digital educational activities can become a potent educational tool for efficient and effective learning. These tools allow children to take advantage of new learning platforms and effectively reach new knowledge through activities related to their immediate interests and real-life scenarios in learning domains, such as mathematics. At the Department of Preschool Education, University of Crete, systematic research was carried out in the last years to investigate whether there are compelling benefits to using tablet-type devices in preschool education to implement teaching reform proposals to implement the Realistic Mathematical Education in kindergarten classrooms. The findings propose mobile devices' integration, running developmentally appropriate apps, in kindergarten classrooms. These apps were based on the three levels of Realistic Mathematics Education (RME), targeting fundamental mathematical concepts for the kindergarten level.