The privacy implications of that kind of 24/7 monitoring "would be highly offensive to a reasonable person," according to the lawsuit, which was filed in the Superior Court of California last week.
Companies are increasingly using GPS-enabled technology to track their employees when they are not in the office. This type of tracking is common in vehicles, but is increasingly being used through smartphones, too.
Intermex gave employees smartphones and told them to install Xora StreetSmart, according to the lawsuit. The app, which is available in Apple's iTunes and Google's app marketplace, costs employers roughly $1 per day per employee, according to Xora's Web site. Employees can use the software to clock in and out of work and fill out forms. But it also tracks their movements.
ClickSoftware, the company behind Xora, did not directly respond to questions about the GPS monitoring features of its software and if it stops tracking when users clock out.
Many other apps provide similar services. The TSheets mobile time-tracking app also collects employee location information, for instance, but the "GPS turns off when the employee clocks out," according to the company's Web site.
Arias wasn't allowed to turn off the phone when she was off the clock to avoid being tracked, according to the suit.
"She's a salesperson, so she was required to leave the phone on in case clients had to call," her lawyer, Gail Glick, told The Post. Arias was fine with being monitored during the workday, Glick said, "her objection was to the off-duty monitoring." Intermex did not immediately respond to a Washington Post inquiry about the suit.
The proliferation of GPS technology is making it easier for companies with just a few dozen employees to roll out such tracking. A 2012 study by technology research firm Aberdeen Group found that 62 percent of companies with so-called "field employees" were using GPS to track staff -- a big uptick from around 30 percent of those companies in 2008.
That makes sense in a lot of industries -- if you're in the delivery business, for instance, you want to make sure that employees are taking the best delivery routes and not making stops along the way. But Arias's suit appears to point to the potential dark side of these innovations.
"Employers have legitimate reasons for monitoring their workers, but all too often we see that kind of tracking spilling over into the private parts of their lives," said Jay Stanley, a senior policy analyst at the American Civil Liberties Union.
There currently aren't many guidelines for when it is appropriate to track employees physical location, he said, but the information that can be pieced together from constant monitoring can be incredibly personal.
"When you know everywhere someone's been, you know a lot about their lives -- you know not only where they work and live, but who their friends are, who their lovers are, what doctors they might visit and their specialties, what sexually-oriented establishments they might visit -- the list just goes on and on," Stanley said.
That also opens up the possibility of discrimination, he said. "What happens if an employer doesn't like the choices a worker makes in their personal lives and retaliates professionally?"