A web-controlled device with relay output and an opto-coupler input:
http://www.controlbyweb.com/webrelay/index.html
It needs 5 volts DC at 500ma to run it.
This web page contains also example source code to control this device from Visual Basic, LabView and Linux system (C source code) at
http://www.controlbyweb.com/webrelay/downloads.html
Those code examples could propably be adapted for other applications as well..
Looks like an interrersting product...