How do cellphone signals work?

There are these devices, but they are illegal to own and use as a citizen.

yes, it’s called a cell phone tower… ;-)
The question by itself seemed like you were wondering in general how does the wireless communication work. Which reminded me of an explanation that Einstein gave one time about how does radio work. He said, you know how the telegraph works, that’s like a cat you pull the tail on one end and on the other end the cat makes noise. Radio is just like that, but without the cat.

How Cell Phones work

There are many programs out there for CellID tracking. Here is one called track me.

From a personal use, the user has to opt-in.

Telecom companies have internal tools to do this as well.