Microwave radiation was chosen for wireless due to its ability to cross walls and other organic materials with relative ease. The concerns for safety still continue, without possibilities to ensure it as there are too many factors to consider. However, if the current societies use them everywhere, anyone should also know that microwave radiation is pretty scary, perfectly capable of producing images of what's happening in other rooms at home or in another house.
A usual radar works with the principle of producing radiation and to wait for reflected signals. Then, it's obvious that a modem or a wireless card could be matched with other gear to create mechanisms to see through walls, not very detailed but still capable of identifying multiple details.
Some say that Wi-Fi or alike radiation should be only used for emergency situations. Who sells telecom services, hardware or any related stuff, or who thinks more in conveniences, being accustomed to it for comfort and very commonly laziness, fashion or whatever psychological aspect, could say a different thing. Right, but then, there's no method to know if some signals coming to your location are for a radar, against privacy. At the same time it's proof that the human organism interacts with them.
It allows the door way open. The project is a rather easy one, especially for the availability of the tools. For it, another inconvenience of using these frequencies!