Application: for all ages, System: Android 4.3 or later, Net weight: 15g / 0.03lbx, Battery life: 3 months, Battery: button battery CR2032, Color: white + light gray, Protocal range: 10 m reach on doors, Data transmission: Bluetooth 4.0, iOS7 or later, Size: 33.3×33.3×13.2 (mm) /1.31×1.31×0.52 inches.
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Updated:
Banggood
Warehouse in China.
Link: Sleepace Sleep Tracker
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Additional Banggood coupons:
1. First page
2. Second page
Price history and price alert
Check out price history chart (for all/most countries) for Sleepace Sleep Tracker. The lowest price was: $15.9.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).