We recently acquired a used shop truck for our business but it did not have a built in MPG meter that tells us how many miles per gallon we were getting.  We also wanted to know how it would overall perform as a plow truck, if it would overheat or abuse the brakes.  This is where the Automatic Link Smart Driving Assistant comes in. First be aware that the app is not downloadable from the Apple App store, you have to go the website as directed on the tiny instruction booklet and from there you can download the app.  After creating an account, just go in and plug the "A" device into your vehicle's computer and you are set.You will not get a information on your vehicle until you have turned off your engine.  The Automatic Link compiles the information while you are driving and will not display any information except that vehicle is in driving mode.  However, it can be set to give alerts if you are speeding, overly using or rough braking and rapid acceleration.  These are all things that can hurt your fuel efficiency.After our first trip it took a few minutes to calculate all the information, but our score was 96 out of 100.  The truck is a 2004 GMC Sierra 2500HD 4x4.  After 1 hour of driving, it got 11.1 MPG and we spent $6.85 worth of gas.  It will show a map of your trip and keeps track of all your trips so it can give you a weekly score.  There are a lot of other extras too like Parking Assistant, get walking directions where you parked your car or Trip Timeline tags the places you visit most often.  The Automatic Link Smart Driving Assistant can also be used on more than one vehicle.In regards to turning off the check engine light, my husband is a mechanic and informed me that yes there are gadgets out there that can turn off the engine lights but don't think that it will be a permanent fix.  Once you go to a repair shop and they hook up your car to their computers for inspection, they will see the codes again.  Just a little FYI.Otherwise, this is a terrific gadget that is truly does everything automatically, all you did to do is drive.