I once had the choice to buy a new car stereo with the ability to change it's volume automatically depending on your speed. I was talked out of if by a friend and I regretted it. While diving, I find myself always changing the volume for some reason. When I hop on the freeway, I have to turn it up. When I get off, I have to turn it down. When I stop at an intersection, down it goes. Dang why didn't I buy that other stereo? Well I have an DROID now and there is an app for that! It's call Car Volume Adjuster and it does the trick. I depends on your GPS speed to determine the volume. You can define the max speed threshold and the min and then how many different "zones" of volume you want. You can set a starting volume and you can pick between MPH and KPH. This apps is a little tricky to get working just right. It took me a little bit of trial and error to find a combination that worked for me. I ended up with my max at 55mph and min a 5mph. Four zones and the start volume at 4 notches below max. Each zone seems to just tell the app whether to adjust the volume up a notch or down a notch. Which means that if the first zone is between 5mph and 15mph then when it reaches 16mph it raises the volume up a notch. If it goes back to 15mph it will go down a notch. This works well but to me doesn't seem ideal. I would like each notch to be a percentage of volume rather than just being notch up or down. Having the volume change is actually pretty cool. I can see where some people might find it more annoying than helpful but I'm not one of those people. There is something strangely interactive about music that loudens when you speed up. The app is about $2 and worth it if you use your DROID in the car.