Ankle monitoring for house arrest is not the same as GPS monitoring for sex offenders. It's two different processes and tracking systems.
Sorry to go off topic but here are the different types of monitoring that are offered by the contractor for FL Dept of Correction:
http://www.ptm.com/default.asp?PageID=3
Active, Passive and RF are the most commonly known offender tracking terms describing supervision levels. Pro Tech’s SMART®Ware System now features a fourth mode: the SMART® Alert level. Pro Tech also offers the SMART®ONE - Wearable giving you a body- worn, one-piece option for your offenders.
SMART®RF – the base unit calls the Surveillance Data Center (SDC) every six hours, or upon violation, to report when your offender arrives at and leaves the home.
SMART®Passive – the tracking unit calls the SDC when placed in the base unit, and every six hours while docked, to report daily location and violation information.
SMART®Alert – the tracking unit calls the SDC twice per day under normal conditions to report location; a violation condition turns the unit to active mode and it calls immediately so that the officer is notified in real-time.
SMART®Active – the tracking unit calls the SDC every hour, or at a “ping” from the officer to report location, and the unit calls immediately upon violation in order to provide real-time information.
SMART®ONE-Wearable - Complements our two-piece tracking device by offering one-piece convenience in a common user interface.
Keep in mind, this would also depend on what type of parameters are set up for the individual wearing the device.
Let's take one of the SO's that live close to Haleigh for example, let's say there restriction was not to be within "X" amount of miles/feet from a school. Then an alarm would not necessarily be sent if they were near Haleigh's home unless it was in the "out of bounds" area.
All that being said, FL is in a budget crisis just like many other states and I know for a fact there have been cuts in LE related items budget. So if I were to make a guess, I would bet they are using the most cost effective (nice wording for cheap) version of this.