A bike that has an LED light speedometer? Why not? Check out this cool tutorial on how Arduino was used to make this creation: http://www.instructables.com/id/Bike-Dashboard/.
What could you create using Arduino? Keep an eye out for "The TAB Book of Arduino Projects: 36 Things to Make with Shields and Proto Shields,” by our very own electronics guru Simon Monk, due out very soon! http://mhprofessional.com/product.php?isbn=0071790675.