On Wed, 30 Jul 2008 22:43:46 +0100, Richard wrote:

Does anyone know of a two socket master/slave version?

Just plug an adapter into it. So long as the current flows through the
sensor current, and so long as you watch the total load (which can
exceed the total permitted, so long as you don't switch both on
together) then it's easy.

Alternatively use a remote control switch, such as a cheap radio switch.
Remote control is nearly as much use as automatic.

If you build your own, start with a current transformer. The rest is
easy.