There ought to be a package for this.   I'd like something like this
too - basically, what I want is a device that I can plug into a POTS
line and have it notice that the phone is ringing, pick it up, play a
message, and listen for input, including DTMF.   I suspect that this
can be done with a Winmodem, but of course that would require us to
have documentation, which is something we're not likely to get.   :'(

			       _MelloN_