I see so many of them around today but I am always skeptical of the scientific validity of them. I’m happy to pay a reasonable amount and I greatly value privacy. Main thing for me would be trying to improve memory.
Any recommendations are appreciated! If I need to go out and buy a DS and a copy of Brain Age, so be it.
Tetris. IIRC there are some very positive studies backing it. There is even something called the “Tetris Effect” (not the game).