Favorite device of Peter Gamma from www.petergamma.org for practicing meditation?

Dilgo Khyentse Yangsi Rinpoche practices meditation without a device: But since Peter Gamma is a physiologist, we wants to have a least one physiolological sensor device for practicing meditation. He currently uses a Garmin watch: But he is not happy with it. Which scientists exept Rob ter Horst use smartwatches for scientific studies? His favorite …