Wearable projector and camera (PROCAM) interfaces, which provide a natural, intuitive and spatial experience, have been studied for many years. However, existing hand input research into such systems revolved around investigations into stable settings such as sitting or standing, not fully satisfying interaction requirements in sophisticated real life, especially when people are moving. Besides, increasingly more mobile phone users use their phones while walking. As a mobile computing device, the wearable PROCAM system should allow for the fact that mobility could influence usability and user experience. This paper proposes a wearable PROCAM system, with which the user can interact by inputting with finger gestures like the hover gesture and the pinch gesture on projected surfaces. A lab-based evaluation was organized, which mainly compared two gestures (the pinch gesture and the hover gesture) in three situations (sitting, standing and walking) to find out: (1) How and to what degree does mobility influence different gesture inputs? Are there any significant differences between gesture inputs in different settings? (2) What reasons cause these differences? (3) What do people think about the configuration in such systems and to what extent does the manual focus impact such interactions? From qualitative and quantitative points of view, the main findings imply that mobility impacts gesture interactions in varying degrees. The pinch gesture undergoes less influence than the hover gesture in mobile settings. Both gestures were impacted more in walking state than in sitting and standing states by all four negative factors (lack of coordination, jittering hand effect, tired forearms and extra attention paid). Manual focus influenced mobile projection interaction. Based on the findings, implications are discussed for the design of a mobile projection interface with gestures.