Mobile computing and wireless communications continue to change the way in which we perceive our lifestyles and habits. Through an extensive literature review of state-of-the-art human-computer interaction issues in mobile computing (Mobile HCI), we examine recent pertinent case studies that attempt to provide practical mobile capabilities to users. We thus contribute to the reader a primer to the philosophy of developing mobile systems for user centred design. User centred design elicits the needs and requirements of end users. Its purpose in mobile systems is to enable useful computing and communicating experiences for diverse types of users, anywhere at anytime and on demand. We shall therefore illustrate to the reader some of the key constraints of mobile devices such as limited visuals, contextual awareness and mobility itself, and more importantly how they can be overcome through innovative design and development.