This is an app that uses the iPhone’s built-in motion sensors to overlay head position animations onto videos of nystagmus.
By using the front-facing camera, users can record their own nystagmus. In this mode, the screen itself serves as a light source.
When using the rear-facing camera, the iPhone can be fixed in front of the eye with a stabilization device, allowing for shake-free recording of eye movements. 
Settings such as exposure, zoom, and LED brightness can be retained.
Videos are displayed in a list sorted by the exact date and time of recording (year, month, day, hour, minute, second). Tapping a video plays it, and swiping left deletes it. The videos are saved in an album named “iCapNYS.”
The app can also transmit iPhone gyroscope data via Wi-Fi. This feature is designed for the Windows software “CapNYS,” which records nystagmus and head position; CapNYS receives and utilizes the data.

Additionally, the app monitors the iPhone’s motion (pitch, roll, yaw), and if any axis exceeds a preset threshold, it triggers a beep and vibration. This function is used during vestibular rehabilitation.