The usability of mobile services is degraded while moving, since users cannot pay enough attention to the services in such dynamic and complicated mobile environments. Mobile and wearable services should be appropriately designed to handle human factor issues, otherwise fine user experiences cannot be offered. In this paper, we discuss design issues in mobile service development from a human factor point of view, and propose a design framework to overcome the challenges. Our approach provides two interaction modes (i.e. simple interaction mode and normal interaction mode) to mobile services, in order to allow a user to keep using the service without frequent interruptions while moving. Also, a service's events are simplified in order to support several modalities so that a user can be notified in the most suitable way according to the situation. To evaluate the feasibility of our approach in field experiments, we developed a pedestrian navigation service as a part of the framework. The results showed that the simple interaction mode successfully decreased a user's cognitive load to the service. Also, future directions for further improvements are discussed based on comments and feedbacks.