I'm sure some systems are vulnerable to this (although the mic might mangle the DTMF). After all until the late 80s the entire phone system was vulnerable to th

I'm sure some systems are vulnerable to this (although the mic might mangle the DTMF). After all until the late 80s the entire phone system was vulnerable to these kinds of attacks because it used in-band signaling http://en.wikipedia.org/wiki/Blue_box http://en.wikipedia.org/wiki/Blue_box