Just as Web MD is the Dr. Gregory House of internet diagnostic tools for human health; there should be a Garage MD for diagnosing car troubles. And, there should be an app for that.
Imagine this, a web-based tool that can be accessed via a computer browser, mobile browser, or mobile app that takes all of your car's symptoms and diagnoses the problem for you. Or even better, listens to your car sounds (i.e. Shazam) and can tell you exactly what is wrong. How awesome would that be?
I honestly hope someone steals my idea and makes it happen, they don't even have to give me any credit, I just want the app to exist and work properly.
Update: But if you want to throw some cash my way I am NOT closing the door on the idea.