If you spend enough time browsing eBay to disassemble interesting electronic devices, you will surely see some suggestions for suspicious devices. This is how I recently discovered these miniature GPS jammer that plug directly into the car's 12v socket. It can be delivered to your door for less than $10, and it seems to be the perfect device to tear apart in the name of science.
Now, you may want to know what legal uses such equipment might have. As far as I know, no. The only reason you want to interfere with GPS signals in and around the vehicle is if you want to avoid things you shouldn't do. Maybe you are driving a haunted company car and want to drive two or two hours in the parking lot quickly, or you want to turn off the built-in GPS in the car so that you can take it to the car shop after stealing it long enough. You know how to do it.
However, we will not delve into the potential evil causes of this device. Hackers have never been too picky about the equipment they want to research and test, so there is no reason to start now. Instead, let's use the hardware in this gray area to test the drive and see what it does.