Lully, the YC-backed startup that built a device to help prevent night terrors, is today announcing the close of a $2.1 million seed round. The company is also presenting at the Highway 1 Accelerator demo day tomorrow, with plans to launch the non-beta generation of the device at the end of this month.

Lully is a device that pairs with a smartphone app and is placed under the mattress of a child’s bed. At a certain time in the night when night terrors are most prevalent, the Lully app will remind the parent to go turn on the device.

It vibrates for a while under the child, preventing the sleep patterns that often lead to night terrors, and ultimately giving both the child and the parent a way better night’s sleep.

Lully shipped the beta version of the product (described above) a few months ago to 150 beta tester families. They tracked 5,000 nights of sleep and ended up seeing a 70 percent average improvement in the way kids are sleeping with the device, with an 80 percent reduction in nightmares.

The new version of the product will no longer have manual switches for parents to turn on and off, but will rather be an entirely automated process. In other words, Lully will know when the child is about to go into a bad sleep pattern and turn itself on to prevent such a thing.

But beyond automation, the team at Lully is focused on solving different sleep problems in children. For example, 75 percent of infants between the ages of four to six months are unable to sleep through the night, even though they should be able to at that age.

Lully’s next device will likely address this age group, as well as small kids with night terrors, in a more automated way.