This kinda stuff is a dystopian nightmare that can also be used to keep oppressed populations inside of a nation's borders, in even-more-wrong hands.
Well... assuming they don't break (or otherwise fail to function as the DHS desires).
There's also the likely expense and hassle of making this stuff actually widespread enough to cover a large border, the inevitability of "blind spots", the fact these probably vulnerable to signal jamming, the risk of sabotage, etc.