Mobile-enabled sleep tracking company Rythm, a startup with offices in San Francisco and Paris, has raised $4 million more from Laurent Alexandre and Xavier Niel. This brings the company’s total funding to around $11 million.

[Correction: This article has been updated to better reflect the total funding amount raised by Rhythm]

The company’s CEO and Cofounder, Hugo Mercier, told MobiHealthNews in an interview that he first began working on developing this technology while studying for his masters at Ecole polytechnique. He was particularly interested in the human brain at the time and sought out ways to spend more time researching it, which led him to meet a team of researchers who were just starting a project on sleep. Rythm was founded in July 2014.

Rythm has developed a connected headband, called Dreem, that tracks the user’s brain activity using EEG while they sleep. It sends this data to a companion app that gives users information about what time they fell asleep, how long they slept, their sleep stages, and their sleep history. The headband also uses sound stimulations while a user is sleeping to improve their quality of sleep.

Dreem is now a functioning device and system, Mercier said but he doesn’t expect to launch it publicly until the beginning of 2017. In the meantime, Rythm will run a limited release of the product, selling 500 to a select group who will provide feedback about the device and app. Mercier said he wants to spend time with users to understand what they are expecting.

“Basically the topic of sleep is really complex,” he said. “Everybody sleeps differently, everybody has different expectations. So to come up with a product that is mature enough to cover the largest amount of needs, we have to spend some time with the first users.”

Mercier said Rythm will choose users for the beta launch based on how motivated they are to use the product. It will cost $349, which includes the headband, access to the app, and all future updates. While Rythm hasn’t finalized the product’s future commercial launch price, Mercier said it would be somewhere around its beta launch price.

There are a number of other companies that have developed EEG-tracking devices — MobiHealthNews included a few in a round up of nine head-worn health wearables a few years ago.

More than any other sleep monitoring company, the now defunct Zeo perhaps bares the most striking resemblance to Rythm. Boston-based Zeo was a high profile sleep tracking company that shut down in 2013.

Another headworn device company, Melon, which developed an EEG-tracking headband company, was acquired by Daqri, an enterprise augmented reality company, in February 2015 for an undisclosed amount. Melon said at the time that its team would continue working on fulfilling outstanding crowdfunding orders for its Melon headband and on developing the second iteration of the device, even as they also advise on the incorporation of Melon's technology into the Smart Helmet.

Some other similar ventures include Bethesda, Maryland-based BrainScope, which raised money last year, as well as Intelliclinic, and Emotiv.