This paper tape fiddling made me wonder if anyone ever
made a cassette
 tape interface that emitted RS232 signals and looked to the computer like
 a paper tape reader/writer. 
    Hmmm....You are a bad guy, David! Now I'll have to think about it :o)
    Easy path: two tone detectors, going to a microcontroller who store the
data read from the tape and send it in RS232 way. A very simple AVR
microcontroller can do that ;o)