Perhaps include a stethoscope and/or an ekg machine that lets you hear the subject's heart. Their heart would beat faster relative to their arousal, but it would have a reasonable BPM cap to stop things from glitching out and spiraling upwards. Species specific heart rates would be interesting as well (avian species might have faster heart rates. dragons would be slower, etc) but not necessary. I guess this files under general medical fetish, but cardiophilia is a particular aspect of the fetish that deserves extra attention.
Customer support service by UserEcho