Making a car difficult to steal

So far as tracking a cell, you don't NEED to. Your car is stolen, call the police. Tell them about the cell and they can have it tracked.

If I get time, I'l try and find out some info on this, but I don't think you need anything special. The type of cell might help. Some of the (older) cells will work on a car adapter WITHOUT a battery, so you don't need to worry about the battery going defective.

Of course if they unhook the battery "just because" that isn't good

Forget Lojack. Someone suggested it, but their coverage sucks. You don't have to get "very far" into the "country" to lose Lojack.