Cars collect some interesting data...
A while back I hooked up my Toyota Corolla to my laptop and accessed the on-board data. Quite interesting and revealing.
For instance, it reports the actual tire/tyre pressure for each individual tire. However, the dashboard indicator is just a simple light that will merely show a general "one of your tires is below the threshold". No details even on which tire/tyre. It would be trivial and inexpensive to show those details. But for that I'd have to upgrade to a much more expensive model, of course.
The most intriguing metric, however, is the weight of the front passenger. So far I have resisted the temptation to install an LCD in the dashboard to display that value... ;-)