Has anyone here used one of those remote serial units that connect to your computer across an ethernet network?

I have a client that uses a keyless entry system at a sports club, and he is able to use a usb<>serial adapter on his laptop to plug in and download the logs of who has been into the building.

He would like to do it from home so i suggested that he use an old laptop and teamviewer.
But since the site is solar powered - they only have a 120 watt panel and 100ah battery to run the lights, it cant use much power.

So I was thinking perhaps if he used a serial <> ethernet converter, we could install a broadband connection with enough solar power to run the router and a port forward to a converter which would use much less power than a 25 watt eee netbook.

Does anyone here know if they work via a port forward in a router?

I am assuming they are all based on the same generic chipset with rebranded drivers like most serial/sound/anything cards you buy today.