This Positive Technology Journal article looks at the Heart Chamber Orchestra: classical musicians who use their heartbeats to control a computer composition and visualization environment. From the article: "To my best knowledge, this is the first example of "group biofeedback".
The musicians are equipped with ECG (electrocardiogram) sensors. A computer monitors and analyzes the state of these 12 hearts in real time. The acquired information is used to compose a musical score with the aid of computer software. It is a living score dependent on the state of the hearts.