I’ve said this before, if you can access something in your home from outside, someone else can probably do so as well. The only real question is how easily?
The reality is you can never make something like this totally impenetrable and useable. But the current security level of many of these Internet of Things devices is so low that it almost doesn’t exist. If you’re thinking of hooking up your home in order to control and monitor it remotely, do your homework.