I think what you need is a device called "Human Touch" from C-Lab. The Human Touch connects to the C-Lab Unitor units which also provides extra MIDI ports and SMPTE ports.
The Human Touch has a built in microphone which will listen to a manual "tap" and adjust tempo accordingly. (This is what I remember from reading the literature)
Unfortunately, the Unitor and Human Touch units are very hard to find. Expect to pay a bundle for them. And both units will only work with C-Lab's Creator or Notator software.
