Not specifically an “automotive” app. but ShuffleMonkey provides a great (and safe) way to listen to your music and lock onto an artist, genre, etc. with just a button press.
http://www.mycarprojects.net
has an Android only app. But it keeps track of repairs for multiple vehicles. It has a Gas mileage log. There are preset repair “Jobs” available. its FREE. You are able to change the job intervals in time and mileage. Plus you are free to add your own. Once your vehicles are added, you can add the expected annual mileage. It will once a month increment the mileage by 1/12 of the annual mileage. If any scheduled service is due. it will email you. there is a mobile site for non android devices.
When are we going to see your worthless app for Andriod! I need to add it to my garbage section. 
Garrett (Honeywell) BoostAdviser turbocharger selection tool. I got it not for my car (a Camry) but since I was taking a IC engines course. Seems pretty cool but requires a bit of knowledge to use (air to fuel ratio, etc). Honestly haven’t really used it yet
I’m late to this thread, but I use Kilroy to post to my buddies where stuff is happening (cheap gas, cool cars etc). Ok and some people post speed traps, but I don’t!
I am not wanting to see computers in my car as I have to guide people through tec support issues like ok is the computer plugged in. Yes but the power is out, does that matter? I have not found Windows a reliable operating system, and I want that in my car! NOT! So a bud says to me his dad bought a new car, it has the on board screen, no cd player but a usb port, what can I do with the usb port, “no clue sorry” I am starting to feel like those old guys when the vcr was flashing 12:00 it was time to call a kid for help!
Re-opened.
A public radio announcer wrote a great app for getting your tire pressure right on the first try, instead of trial and error. He calls it Deflator Mouse!
When I bought a new 2012 Civic, it was really pushing gas mileage. On trips I used to keep track on paper, but surely there’s an app for that! There are several; I chose Mileage Keeper. Very basic: it takes your odometer reading and gas amount to calculate the mileage; it will also take what you paid and save it as $/gal. It has a space for notes (the car calculates the mileage, too, and I note it there to compare: usually within .5 mpg). It also keeps a running tally: just shy of 20,000 miles, I average 36.5 mpg, used 519 gal, and spent $1961. Whew!
So: nothing fancy, does just what I want and no more.
where would I find the 5,000 free classics they mentioned.?..thank you
Although I don’t hit the strip, I’ve used Dynolicious to figure out my WHP. Don’t have many mods but it is good to know vs using the ol “butt dyno” :D. Also fun to see your Gs and to just keep track of your car in general.