Hi Ian and thanks for your reply.
Yes, this is a "greenfield" project so I have no restrictions, whatsoever.
I am essentially trying to build or buy the cheapest device possible that would convert the revs of a running engine into a USB signal. I saw the PCB you linked to but it has an RS-232 connector, not a USB...
My laptop does not even have an RS-232 so I would have to buy an additional RS-232 to USB adapter or something like that.
Imagine that when the driver steps on the gas and perhaps the alternator generates more power to provide more amps to the battery, my device will send a bigger integer through to the USB.