Of course you don't _need_ it, but it's a useful convenience. Due to the layout of our house it was quite hard to hear my toddler if he was crying in the middle of the night - we often wouldn't wake up to it. So the monitor was very helpful.
Why on earth do you need an app and a camera? The same basic VTech audio monitors that are basically the same for many decades now work great, don't cost a fortune and there's no question of "where is this data going?" It's all just a big cash grab for people who need chincy tech toys for a non-problem that's better solved with way more simple kit.
