> generating DTMF tones yourself and injecting them into the audio stream?
When I was an undergrad I had an audio file for each digit and a winamp playlist for each of my frequently dialed numbers. I'd hold my (landline) phone against the computer speakers and double-click the playlist to dial. I'm sure I spent more time setting this up than it ever saved, but it was somehow pleasing that this ridiculously over-powered speed dialer worked.