The abundance of smartphones, with their growing capabilities potentiates applications in numerous domains. A typical smartphone nowadays is equipped with an array of embedded sensors (e.g., GPS, accelerometers, gyroscopes, RFID readers, cameras, and microphones) along with different communication interfaces (e.g. Cellular, WiFi, Bluetooth, etc.). Thus, a smartphone is a significant provider for sensory data that awaits the utilization in many critical applications. Primers of this vision have demonstrated success, both in the literature and application's market. In this literature review, we present the main motivations in carrying these smart devices, and the correlation between the user surrounding context and the application usage. We focus on context -awareness in smart systems and space discovery paradigms; online versus offline, the femtocell usage and energy aspects to be considered, and about the ongoing social IoT applications. Moreover, we highlight the most up-to-date open research issues in this area. (C) 2017 Elsevier B.V. All rights reserved.