Updated below with statement from Fitbit.

A California man has filed a class action suit against Fitbit, alleging that the company's sleep tracking is inaccurate and constitutes false advertising. The timing of the suit, just days after the announcement of Fitbit's plans for an IPO, is suspect, but the premise of the case is important.

James Brickman, who bought a Fitbit Flex in 2013, doesn't allege any specific harm that may have come to him as a result of inaccurate sleep tracking. But the case cites a 24-person 2012 study from the journal Sleep and Breathing as evidence that Fitbit's sleep tracking is inaccurate, particularly with regards to the amount of sleep recorded per night. The study compared a Fitbit device to polysomnography and actigraphy, and found that it over-reported sleep compared to both.

Correction: The original version of this article listed the journal in question as Sleep Health.

The lawsuit uses the price difference between the Fitbit Zip (which doesn't track sleep) and the Fitbit Flex to calculate the value the consumer paid for sleep tracking at $30. It alleges that the case "involves more than 100 class members and more than $5 million in controversy."

At this point, most fitness trackers, not just Fitbit, purport to track sleep. But most just use the accelerometer combined with an algorithm, and few have clinically validated this functionality. (A notable exception is Intel's Basis Band, which found that its device performed similarly to polysomnography in a small study last year.) A case like this could encourage companies to put more energy into validating their sleep tracking.

There are a number of ways Fitbit could respond to the suit, including attacking the validity of the 2012 study which, in addition to having a small sample size, couldn't have used the Fitbit Flex, a device that launched in 2013. Or they could make the case, as they did in response to criticisms of step tracking accuracy earlier this year, that consistent tracking of personal trends provides value to customers even if it's not objectively accurate.

But given the opportunistic timing of the suit and the planned IPO, Fitbit may quietly settle out of court, which may or may not have an effect on the standard to which the activity tracker space holds its sleep tracking functionality, or the language with which they advertise it.

Update: Fitbit told MobiHealthNews by email that they intend to fight the lawsuit.

"We do not believe this case has merit," the company wrote. "Fitbit strongly disagrees with the statements about the product and the Company contained in the Brickman complaint and plans to vigorously defend the lawsuit. Fitbit trackers are not intended to be scientific or medical devices, but are designed to provide meaningful data to our users to help them reach their health and fitness goals."

Fitbit has already emerged victorious from one lawsuit: a copyright battle with British competitor Fitbug. Fitbit won the case, although only on the basis that Fitbug waited too long to file it. Fitbug appealed the ruling in February.

Another similar but unconnected lawsuit this week could also have repercussions in the tracking space. Myrna Arias, also from California, is suing her former employer Intermex after they fired her, she alleges, for uninstalling an app that would enable the company to monitor her location 24/7. In this case, the app, Xora StreetSmart, was designed to help companies keep tabs on remote employees, but the case could be of interest to companies that provide GPS-enabled fitness trackers for employee wellness purposes. Employee privacy in health programs has already been the subject of at least one lawsuit, when the Equal Employment Opportunity Commission sued Honeywell over its biometric screening program last fall.