Materials needed for a GPS speed switch

Using Arduino Project Guidance
1

Hi!
I'm new to Arduino so I hope someone can help me understand what materials I need (arduino board, etc.) for a project I want to do.

What I want to do is create a switch on my motorcycle that automatically turns on or off depending on my speed. Ex. if I'm going over 20 mph I want it to be on and off at less than 20 mph.

So far I think I can use a gps for the speed input.

What I need to know is what hardware I would need and how that hardware would be set up.
Can the arduino be powered by my motorcycle battery/charging system? (12v/14v)
How can I connect the 12v accessory to the arduino to respond to the switch?
Can this even be done?

Thank you in advance for your response!

2

It is certainly possible to program the Arduino to read the GPS output and determine your speed, if the GPS unit has a clear view of the sky.

How the Arduino would control a 12 volt device depends on the device, so you'll need to provide more information.