Motion sensor with ethernet are there any cheap once?

What is an cheap way to get a motion sensor to send information to my computer?

This sensor will be mounted in a place where there is no wifi. So i'm thinking about using some form of ethernet. Allthough most chips with ethernet seem rather expensive. around 20-30 $ at this point it becomes cheaper to just buy a raspberry.

The distance between the sensor and the computer will be a couple of miles so i need to be able to transfer it over the internet.

A pair of ordinary wires works well to transmit information, especially from a simple sensor like a motion detector.

jremington:
A pair of ordinary wires works well to transmit information, especially from a simple sensor like a motion detector.

Oh the thing is the distance between my computer and the sensor will be a few miles. So sadly regular wiring wont work

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Don't forget that for the Raspberry Pi to work reliably you'll also need a high quality power supply and a decent quality SD card. That bumps up the cost of the Pi significantly.

If you want to go super cheap, you can get a Nano derivative and a W5100 Ethernet module or an Uno derivative and a W5100 Ethernet shield for much less than what you're quoting.