I have a similar device at home called the "Practice hit" I paid less then $40.00 for it. It has elastic bands at the base to aid the flexible rod that has the tennis ball attached to it. I had to fill the hollow base with sand to give it some weight. Overall, it is not a bad way to learn a new stroke because it allows you to focus on the technique. I occasionally hit for 15 to 20 minutes with it and focus on technique and weight transfer. Not a replacement for actual playing, but it will improve your game if done the right way. It can also give you a great workout in about 20 minutes. I'm happy I bought mine.
Wilson PSC6.1, but lookin for a Tweener.