If I remember correctly, SCOTUS ruled in 2015 that NC’s ankle monitoring program was indeed a search as defined by the 4th Amendment. The court did not rule, however, on whether the “search” was “reasonable” or not because the point was not broached as part of the filing.
It’s a moot point, really. When you are put on GPS monitoring you have to sign a form that essentially says that the state is authorized to execute this unwarranted search 24 hours a day, 7 days a week. I was erroneously put on the monitoring program after my release. Fortunately I was able to get it off but it took over a year.