The device has had many names over many years. It was developed by Lenny Schloss who used to own/run Baltimore Tennis and Fitness aka Hilton.
When I was teaching in Baltimore, I spent a couple years helping the Baltimore Tennis Patrons with their winter and Summer programs and we used this device. Originally it was called something else, then when we had it it was called the Accuhit. Each time, something is tweaked to improve it. Could be as simple as the mounting system or whatever--then the name changes.
Then It was changed to HAL.
now apparently its called the Eye Coach.
Baltimore Tennis and Fitness used (maybe still do) offer free 30min lessons, majority of which would be spent using this device to create muscle memory. Then they would go into dead ball feeding and slowly into rallying.
It can help develop a feel for topspin bc its a visual as well as a kinesthetic aid. Also helps establish timing.
there are a ton of drills to use on the device.
I recommend using an older racquet bc if you mishit, and hit the frame of the device, u can break strings or even a frame.
Its a cool device, just never caught on mainstream teaching