Most cars nowadays (especially rentals, which I’ve been in a lot lately) have 1/8″ AUX inputs for an MP3 player. When I had just an iPod, this worked great. Now that I have an iPhone I found my standard 1/8″ to 1/8″ extension cable that I’ve had in my cable go bag wouldn’t work. There’s no way I’m going to spend upwards of $20 on an iPhone adapter cable to get around Apple’s design mistake. Five minutes with the Dremel and I’ve got a handy DIY iPhone adapter cable (and lots of little rubber bits all over the place)
And don’t forget the little bits of rubber in your lungs, too! :)