The paper presents the design of a mobile assistant for runners. We propose visual and auditory user interface for a mobile assistant, called Mobota. The system supports navigation on a new track, provides competition against a virtual rival, monitors real time user performance, entertains and encourages runners. We introduce entertaining and inspiring community notes that convey emotional messages from other sportsmen who exercise on the same track. The design and evaluation of Mobota provides an insight into the specifics of visual and auditory design of running assistants. Categories and Subject Descriptors H.5.2 [User Interfaces]: Graphical user Interfaces (GUI), auditory (non-speech) feedback, screen design General Terms Design, Human Factors. Keywords Training assistant, mobile sports, mobile UI, auditory design.