This is an item that allows you to hit by yourself and with out a wall. There are various types out there. I had the Tourna model years ago. I've noticed that many places are out of stock.
For those that have used this...did you notice if it changed your swing path? Curious as I would like to get another one but not at the expense of it changing my game.
I have had one of these for two years now. I really quite enjoy using it. I wouldn't say I can hit a proper stroke or very high power, but I can use windshield wiper forehands, really brush up on the ball and get a lot of spin going which is fun enough. As someone else commented they do pick up pace in the opposite fashion to normal shots, they get faster the closer they get to you.
Look, it isn't rallying, it isn't a proper replacement for a match or practice, but I find it fun enough in the back yard when I have been unable to find a buddy to play against for a couple of weeks.
Most people make the mistake (as the video showed) of standing really close to the base. Put it a good way ahead of you, say 5 or more meters. That way the cord can extend fully away from you (the ball will be a long way out when hit properly) and can do the same coming back towards you. This gives it slightly more realistic trajectory and movement, as well as allowing you to you use proper footwork and better stroke styles, rather than rushing like crazy and hitting a variety of weird and whacky shots, as the people in the video were!
I bought thicker elastic for mine. Much more durable and a far better snapback which made it much more useful.