Are you a fan of the Back to the Future movies? So am I! This application is a plugin for Torque, an application that connects to your car via an OBD-II adapter. You need it to use this app!
OBD DeLorean Speedometer does what it says: it's a Back to the Future-styled DeLorean speedometer (the digital one Doc built) that connects to your car and displays its speed in real time. With optional time travel sound effects!
Warning: this is not an ACCURATE speedometer and should not be used as such, despite usually not being too far from the actual speed. Keep an eye on your genuine car speedometer. Seriously.