Computer Feedback in Meditation
Biofeedback programs just take data such as heart rate, blood pressure, etc... and display them on a screen so that the person can see them. The underlying theory is that if a person can directly see what's going on, they would be better able to adjust themselves to slow them down.

Because these devices cannot directly access the mental activity of the meditator, I don't see how they could be of much use. Certainly if one is developing some form of calm abiding it might be useful to an absolute beginner, but once they start making progress, even stopping to check the machine readout would be comparatively distracting and would erode one's concentration.