Molly Wood:

EVEN with their high-tech gadgets and computerized machinery, most cars still do a pretty poor job of providing helpful information about things like mechanical problems and fuel use — and of connecting to the devices we use the most, our phones.
 Improvements are on the horizon. Wireless connections are available in some new models, which could lead to more helpful tools. But even for many older models, there is an easy way to get better information about your car, including fuel usage, diagnostics and data about your driving habits.