HOSS,
I am working on a "Patented" Emergency water-cutoff system for Jetboaters, which also serves the purpose of regulating the water pressure coming off the jet automatically with a 12VDC power source (your battery) and regulating proper system pressures. These pressures often depend on engine RPM and pump type/work performed.
There are many manufactures out there that sell gauges and or sensors with many types of signal returns; 1-5VDC, 2-20ohms, 5-40mA, etc.
Check the Grainger catalog for such a device. They have been an awesome source for components of that nature and offer a great deal of help on proper selection of parts.
As far as your other question with regards to location, you might want to contact Froggy and or Greg @ G&S Marine. They have always offered a wealth of reliable information on these types of questions.
~Ty