Sleep-turned-fitness tracker Lark Technologies has raised $3.1 million from undisclosed investors, according to an SEC filing first spotted by TechCrunch. The filing lists Anis Uzzaman, general partner at Fenox Venture Capital, and Weili Dai, president and co-founder of the Marvell Technology Group in China as related persons on the raise. Fenox Venture Capital is a previous investor in Lark.

This is Lark's second funding raise. The company raised $1 million from Lightspeed Ventures and undisclosed angels in May 2011.

Lark debuted in 2011 with a silent alarm armband that vibrates to wake the user without waking anyone around them. The $99 alarm clock is also a quantified self offering, which tells users their sleep quality, sleep time, and number of times awakened. The company has also added a pro version for $159.99, which offers sleep coaching in addition to other features.

At the beginning of this year, Lark added LarkLife, a fitness tracker wristband, to its product portfolio. Lark Life adds activity tracking to the sleep tracking functionality of the original Lark, and the connected app also lets users track and manage nutrition and productivity. It sells for $149.99.

The death of competitor Zeo, which also offered sleep tracking and an alarm clock tied to the users' sleep schedule, called into question the profitability of sleep tracking as a consumer play, but it also opened up the field for companies like Lark. It is notable, however, that Lark's diversification into fitness tracking came shortly before the Zeo news was made public.

Although the company has been fairly quiet, it does have a retail presence, showing up at the Apple Store in MobiHealthNews' survey of brick-and-mortar digital health tools in June.