Understanding Diagnostic Port

So I understand modern cars have these diagnostic port, u plug in a gadget, BAM! tells you what's going on.

Question#1: Is this standard for all cars/brands, I mean is, one tool suffice for my Honda as well as my Mercedes?

Question#2: For street-Joe, knows enough cars to be dangerous, how about a cable to my iPhone and the App got all the smarts to explain all the archaic diagnostic codes am looking at?


Can it be this easy?
 
Solution
Most passenger vehicles use the OBD2 standard. This is a plug usually located under the dash near the drivers seat.

They have a few Bluetooth OBD2 transmitters that plug into the port and transmit data to your phone.