Henri, indeed, I could see the trams in Helsinki, but not Busses so far. I haves asked HSL about the plans to provide the GEO position for more lines.
As a suggestion, what about showing some icon in the middle of the map (own position). I was also thinking, if it would make sens to let the user choose whter he/she is in a bus or tram, type the line no and publish the geo position for other users. Too bad that this would require an extra server component :/