Bad for those that don't have speakers as it can develop in a direction that not using mainly useless gadgets as suspect.
People involved in future crime: Victim, supect, Amazon, Google...
Unfortunately this not all fiction, it is already happening for social media. Some countries require you to turn over your social media accounts at the border. If you don't produce a Facebook/Instagram/Twitter account you are immediately a suspect.
And they're fast asleep because 11 pm is not the time to be awake for them. How will the speaker save them? By recording snoring noises and storing that?
Certainly not enough to convict someone, but there could be other unfortunate factors.
However, if you allow questioning to proceed, you cannot always stop the questioning in the middle with the same rights as above.
Also, in the US, improperly obtained evidence is seldom thrown out of court for some reason. Arguing that a warrant wasn't obtained doesn't always work.