> 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.
Back in the days of phone line modems, there used to be a program that you could type in a number, the modem would emit the corresponding tones, and then you could pick up a phone and it'd already be connected. I can't remember what the one I saw was, but I'm sure there were multiple different ones, and I also vaguely recall there were dedicated physical machines that could before that.
You could do this with any terminal program. Your modem won't emit any noise until it hears a carrier tone, so you could just dial, pick up the extension, hang up the modem.
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.