For decades, linguists have introduced theories related to the process of acquiring second languages. As the world rapidly changes, particularly because of the integration of emerging technologies in everyday human activities, theories that were primarily based on traditional ways of teaching and learning different academic subjects which include languages, i.e. first and second languages, should be evaluated and updated if necessary in order to keep them relevant. Different geographical locations, socio-economic and political changes should also be considered when evaluating those available theories. In the context of the current world characterized by the use of modern mobile technologies, this book provides the detailed literature on technology for language learning and theories of second language acquisition, and it evaluates the validity and relevance of Krashen’s Input Hypothesis based on the case of Rwanda, a small landlocked, non-industrialized monolingual country of Africa, which shifted from its colonial legacy ‘French’ to the liberation anthem ‘English’ as the foreign language used as a medium of instruction at all levels of education since 2008.