Yeah, basically (unless really necessary), I'm looking for something
ready-made. I need 2 units & they need to get installed on 2 ocean going
ships for about 2 or 3 months for some testing of satellite transceiver
performance vs sea state, so it's

Here's a link that might be useful, I don't know what the prices are like.

http://www.datawell.nl/products_motion_sensors.html

Dennis