San Francisco-based Sproutling has raised $3.9 million, according to an amended SEC filing. The company started the round in August
2013 and has raised at least $6.5 million total to date.

Existing investors include First Round Capital, Forerunner Ventures, FirstMark Capital, Accelerator Ventures, Lemnos Labs, BoxGroup, and Napster co-founder Shawn Fanning.

Sproutling has developed a health sensing device that a baby wears around their ankle. The device measures heart rate, skin temperature, motion, and the baby's position. It also sends this data to a companion app on the user's phone and lets parents know if the baby is sleeping soundly or if there is some kind of issue. The app predicts when the baby will wake up, too. And when the baby does wakes up, the app relays whether the baby is calm, fussy, or angry. 

The device can be inserted into one of three ankle straps so that the device still fits as the baby grows. Sproutling's wireless charger is also equipped with sensors that monitor the baby's environment -- room temperature, humidity, as well as sound and light levels -- to improve the baby's sleep.

In August 2014, the company launched a "preview release" of its baby monitor. Sproutling explained that unlike a beta, a preview release makes a limited number of fully tested devices available for purchase. The preview is designed to help the company understand the market demand. Devices were available for $249 on the company's website at the time and Sproutling said they would ship the monitors in March 2015. The device will retail for $299.

Sproutling Founder and CEO Chris Bruce previously built mobile platforms at One Medical Group and WellnessFX. Other Sproutling employees are alums of Google, Apple, and Amazon.