Narbis Edge electrochromic smart glasses only. Use standalone for guided breathing sessions, or pair with an ear clip sensor (sold separately) for full HRV biofeedback training. Also compatible with Muse 2, Muse S, and Athena for neurofeedback. Electrochromic lenses respond in real time Standalone guided breathing mode included Companion app included (iOS/Android) Ships in 30–60 days (currently on backorder)