A personal digital key (e.g., which can be carried by a human) contains a memory having different service blocks. Each service block is accessible by a corresponding service block access key. As the personal digital key (PDK) moves around, it is detected by sensors. The sensors report position data, thus enabling location tracking of the PDK. The sensors also provide a data path to various applications. An application that has access to a service block access key can therefore access the corresponding service block on the PDK. The sensors themselves may also contain service block access keys.