not a dev, but just wanted to comment on what Mato_xXx said about the chinese app that uses SMS.. if someone were to make an app, in some places (not sure if this is the case in China) data is more than SMS and vice versa.. and i know that those chinese made GPS car tracker devices work like this:
-uses GPS to record location
-checks every so often for location changes
-if location changes SMS gets sent to a number you pre-programmed into it every several seconds
these devices come with apps you can download to track the location of vehicle using google maps. Here is an example of said device:
(i am a new user and was unable to post links, but serach for "gps vehicle tracker" in google or serach amazon)
these things meet the criteria of your first requirement without the use of data (it instead uses SMS). If someone were to make a car security app, they should add this as a feature (location via SMS) because depending on what provider you are using you might run out of data or you could go over you data limit and amass a large bill... this would be an issue for people in Canada as we have some of the most expensive cell data in the world
I think what needs to be done is an app that can be installed where you can make it so the car wont start without some kind of authentication entered via your android device + the key..
what I think you were talking about when you said your friend found a key that would start your crown vic is the crown vic fleet key, which will start any crown vic (and usually the glove box and the trunk) ; (again, i am a new user,cannot post links, but serach google for "crown vic fleet key")
and because your vehicle is an old crown vic, its not going to have any wireless daig features so im assuming you'd have to buy some kind of hookup adapter for OBD2 to interface with your car.. but if you make any progress with this project please let us know..