There are far more obvious ways to know if someone is home, from thermal sensors, looking in windows and knocking on doors, or park outside and just watch.
Further if the police want to know if you’re home, it’d already game over.
It’s never too early to start thinking of the implications of technology. It’s not inconceivable that in a few years every crooked small town cop will have access to tools straight out of science fiction- tools that started out as innocuous research.
X-Ray vans (2015), https://www.foxnews.com/science/x-ray-vans-security-measure-...
> The Z Backscatter Van (ZBV), manufactured by American Science and Engineering .. can also see through clothing and into some buildings, are raising privacy concerns as well as questions about health risks ... the van -- which looks like a standard delivery van -- takes less than 15 seconds to scan a vehicle; it can be operated remotely from more than 1,500 feet ... vans range in cost from $729,000 to $825,000.
All of these have the disadvantage that the observer can be spotted - there exist numerous articles on how to spot cameras because sketchy AirBnB hosts placed hidden cameras in bedrooms and toilets. A radio-based monitor however doesn't need line of sight - if small enough, it can be hidden just about anywhere where no one looks, like the interior of a rainwater tank, under the bottom of a trash can, in a roof water drain.