I don't believe it's dangerous at all.

I followed a guided meditation audio initially. It focuses on deep relaxation, lying down and staying very still while you focus on awareness of your body and breath.

I think folks who haven't tried to really relax and connect with their body might be surprised how much awareness and control you can have.

I have a fitbit and I can drop my heart rate quite a bit with practice, I've gotten down to 39 before with breathing and relaxation techniques.