On 28/01/11 13:48, mick wrote:
Anything mains powered with an IP address will do . So your router would be fine. Or any of a large range of "home automation" devices which are networkable (http://home-automation.org/) if you actually want to spend money on gadgets.
Taking another sideways step, you can get a multimeter on eBay for about £30 that has a USB port, although no mention of drivers for Linux. You can also get USB-based dual channel oscilloscopes for not too much money. Something like that might allow you to monitor the power but also have other monitoring uses on the boat should you think up an application. If you're handy with a soldering iron I'd have thought it ought to be quite easy to knock together a monitoring circuit that would give you more information back for your money (start at Maplin, see what toys they have, then google for cheaper ways to do the same thing!)
Another thought is the variety of cheap boxes with current transformers for monitoring domestic power usage; sometimes given away by power companies, although one with a USB connection may cost you a bit more. But again, you might be able to get something more out of it than just the fact that power is available.
All this said, I think you'd be hard pushed to beat a cheap UPS with a USB port for which you'd find drivers and functionality galore in Linux.