At home and at work, I find myself constantly looking up a phone number on the iPhone, then dialing it manually into a wireline phone.

This is because calls made by wireline are cheaper, better sound quality, and lower radiation.

Various watches and data-banks I've owned over the years had the capability of emitting the DTMF tones for a phone number out of a speaker - straight into the microphone of a telephone handset - thus dialing the number for you quickly and accurately.

This function was present on the Apple Newton... so hopefully no technology barrier to doing it on the iPhone.

Get started with code from here:

http://code.google.com/p/iphreak/