This is exactly why I will not be buying a first generation Apple Watch. I have wicked terminal (morning, not fatal) insomnia and currently use a Basis B1 for sleep tracking, so I can assess the effectiveness of various treatment. It has accelerometer, heart rate tracking, skin temperature, and galvanic skin response tracking, making it a fairly capable sleep tracker. However, it is hobbled by several factors: a plastic face that is easily scratched, the inability to see sleep data on the device, poor tracking of sleep onset and awakenings (sometimes misses I GOT OUT OF BED!!!), and terrible support for data export with no HealthKit integration (hell, just to get raw data I have to use the app for their new product the Basis Peak, it isn't available from the website). It also only gets 3-5 days of battery life under light use.
I had hoped the Apple Watch would prove to be a more capable sleep tracker based on early reports about the sensors and data integration, but unfortunately the battery life means it has to charge overnight, and Apple hasn't even included any advanced sleep tracking features. This was a major disappointment. Right now I'm still waiting for a new product to come along...I won't be buying anything from Basis ever again (my B1, aside from the failings above, has been in for warranty repairs TWICE in a year). I've seen a Kickstarter for an EEG solution slated to come out this fall, maybe that'll finally be the tracker for me.