https://www.hdroptech.com/

Price: $149.99

Description:

hDrop is a non-invasive, inexpensive, and easy way to track hydration.

A wearable device able to measure your hydration status in real-time through your sweat.  hDrop measures the changes in electrolytes in your sweat as well as your body temperature in order to provide early notifications to the user.

The SELF Institute