I have been trying to think of a very simple way to load my engine monitoring program at startup, without having to use a ridiculous cassette drive, or a separate computer. I think I have finally found the answer: Custom Cartridges. I SHOULD be able to write my programs to a chip, stick that in a custom PCB, then put that in the Atari and leave it there. This should be the easiest way to load the program every time the computer is started. So far I have found something that may prove useful:
I still need to figure out what IC to put on the board, as well as how to flash it. Will research this later.