The app is a demonstration of smooth pursuit-based gaze interaction. It allows entering characters into a text field by following targets on the screen with the gaze. The significant advantage of smooth pursuit-based gaze interaction is that it works without eye tracker calibration. This property is desirable for instant (and hygienic) gaze interaction with public interaction, such as vending machines and ATMs.
The app is the proof for a scientific publication (Heiko Drewes, Mohamed Khamis, Florian Alt,
DialPlates: Enabling Pursuits-based User Interfaces with Large Target Numbers, MUM '19, doi=10.1145/3365610.3365626). The research question was how many targets a smooth pursuit-based gaze interface can use. The app provides examples for 13 (ATM), 32 (CCITT), 72, 102 (ASCII), and 160 targets.