From the product description, check product page for current description, price and availability:

Gravity measurements without touching the beer!
PLAATO Airlock is a brand-new way of analyzing your ongoing fermentation. This wireless hydrometer and airlock connects to your local WiFi and sends information about your fermentation straight to your phone. You can track specific gravity, fermentation activity, alcohol percentage, and ambient temperature. And you can do so 100% non-invasively, no contact with the wort needed! By knowing the rate of CO2-release, PLAATO Airlock can estimate the Specific gravity and alcohol content of the batch. Best of all you can use it on all types of fermentation; beer, wine, cider, mead, and hard seltzers!

Monitor your batch from anywhere with the PLAATO App!
With the PLAATO App you are able to monitor the fermentation of your batch from anywhere in the world. This gives you time for other things and peace of mind knowing everything is going as it should with your batch. The same app is used to monitor both PLAATO Airlocks and PLAATO Kegs. Track your fermentation and kegerator stock level all in one place.

Features:

Real-time and historical data tracking.
During the fermentation, you have access to the essential parameters in real-time, giving you a unique insight into how different strains of yeast work, how temperature affects the rate of fermentation, and much more.

Fermentation management.
Keep track of all your fermentations in one place. Each airlock has its own dashboard, letting you type in batch-specific data. There is no limit to how many fermentations you can track simultaneously or to how many people can access the data.

Know when your beer is finished.
When the BPM (Bubbles per Minute) reaches zero, you can be absolutely sure that the beer is finished fermenting – the yeast has fully consumed the sugars – and you can with peace in mind continue with dry-hopping or cold-crashing.

Integratable to your favorite brewing software.
Get everything in the same place – and track your fermentation directly from Brewfather or other brewing platforms.

The science behind the PLAATO Airlock.
Understanding the delicate and yet versatile processes behind brewing is key to unlock its amazing potential, and produce great products with high repeatability, quality, and integrity. The release of CO2 is directly proportional to the chemical reaction rate – ie. how fast the yeast works.

By knowing the rate of CO2-release, we also know how fast alcohol is produced.
If we know the total volume of CO2 released, we also know the total amount of ethanol produced and gravity.
PLAATO Airlock measures both the rate and the total amount of CO2 generated, and is, therefore, able to measure and estimate:

Fermentation activity
Specific Gravity
We know what all you hop heads are thinking, but can I dry hop!?!
YES! No worries, you can open your fermenter and dry hop as normal. The small amount of CO2 that escapes when the lid is taken off only affects the measurements marginally.

Note: Does not include a stopper. Compatible with rubber stoppers and grommets. NOT recommended for use with small or medium universal stoppers.

Track multiple batches with additional PLAATO Airlocks!

Functions:

Measures Fermentation Activity
Temperature Sensor
Specific Gravity Calculation
Alcohol Content Calculation
100% Non-Invasive
V3 Updates:

Redesigned bubbler. The bubbler is slightly smaller than the previous versions, which allows it to expand in contact with water and remain functional for long fermentations.
Redesigned lid. The lid is flexible, which makes room for the expanding bubbler. It is optimized for extra-long fermentations.
App Features
The free PLAATO app lets you have all your PLAATO Kegs and PLAATO Airlocks in the same place. Each airlock has its own dashboard, letting you type in batch-specific data, including:

OG & FG
Fermentation Activity in BPM (Bubbles per Minute)
Temperature
ABV%
Chart with fermentation rate, gravity, and temp.
Share data with friends
Airlock Specs:

Operational Batch Size: 1-13 US Gallons
WiFi Connectivity
Note: WiFi is only compatible with 2.4Ghz networks and is NOT compatible with routers using WPA & WPA2 Enterprise security.
Free iOS/Android App
Waterproof
USB Powered
3m magnetic USB cable – color may vary (included)
Works with any USB wall charger (not included)