Eye-in-the-sky noun phrase informal
Surveillance above your head or in the sky, such as a camera or a police helicopter
The eye-in-the-sky in the store can prove that I didn't steal your phone.
Eyes-in-the-sky have helped the police a lot in solving cases.
Children or adults often say this phrase to get their friends to join in something, especially to jump into a swimming pool (pond, lake, etc.)
“Last one in is a rotten egg!” yelled Jane, jumping into the pool.