The abundance of smartphones, with their ever growing capabilities, potentiates applications in a multitude of domains. A typical smartphone now 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 of sensory data that awaits the utilization of 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. Furthermore, we highlight the most up-to-date open issues in this area.