Over the years I have been a gadget guy, and I studied biofeedback therapy during my residency at the Menninger Clinic. Temperature, breathing, GSR (galvanic skin response), EMG (muscle tension), and EEG (brainwave) biofeedback are proven effective treatments for anxiety, stress-related illnesses, insomnia, some types of ADHD, chronic pain, headaches, and other disorders.
Biofeedback machines used by professionals are the most effective and the most expensive, and some are available for purchase to use at home.
I recommend you look up Muse, Spire, Thync, Inner Balance Lightning, and Pip on Amazon, read the reviews, the company products websites, and look at the research on biofeedback and meditation through Google Scholar.
For guided meditation I recommend the apps Headspace, Buddhify, Mindfulness, and Insight Timer.