Hydrometer -
A must have tool for any lash artist. 
This very compact device displays time, temperature and humidity in your room. 
It also has alarm and calendar functions. 

Can be placed on a desk or hung on a wall. 
Low power consumption: 1 x AAA battery (NOT included). 
Product dimension: 100 x 108 x 20mm. Weight: Approx 160g.