While driving the speedometer uses the backlit display of your iPhone or Android and reflects it clearly onto your windshield. Other info displayed is the weather, ecodrive (which shows how green you are driving), and the zero-100 mode.
The zero-100 mode is interesting, it shows how fast you accelerate but not entirely accurate it's pretty cool if you have a newer call and want to push it to the max.
The best thing about this app is it's free and highly recommend it to anybody wanting to try this new innovative app out!
HUDY is available on Android as well as on iPhone & iPod Touch.