The space around the body not only expands the interaction space of a mobile device beyond its small screen, but also enables users to utilize their kinesthetic sense. Therefore, body-centric peephole interaction has gained considerable attention. To support its practical implementation, I propose OddEyeCam, which is a vision-based method that tracks the 3D location of a mobile device in an absolute, wide, and continuous manner with respect to the body of a user in both static and mobile environments. OddEyeCam tracks the body of a user using a wide-view RGB camera and obtains precise depth information using a narrow-view depth camera from a smartphone close to the body. I quantitatively evaluated OddEyeCam through an accuracy test and two user studies. The accuracy test showed the average tracking accuracy of OddEyeCam was 4.17 and 4.47cm in 3D space when a participant is standing and walking, respectively. In the first user study, I implemented various interaction scenarios and observed that OddEyeCam was well received by the participants. In the second user study, I observed that the peephole target acquisition task performed using the OddEyeCam system followed Fitts’ law. I also analyzed the performance of OddEyeCam using the obtained measurements and observed that the participants completed the tasks with sufficient speed and accuracy.