I have a couple of devices here that required computer control of their power leads: my (flakey) ADSL modem, and the external AMP for my office empeg.

The empeg remote AMP lead is used to directly drive a solid-state relay I picked up for CND$5 in Toronto, so that one was very easy.

The ADSL modem, when it goes flakey, requires a power-cycle to restore sanity. So my everything-server (web,ssh,dns,dhcp,ftp,nfs,smb,...) now runs a very simple shell script from /etc/crontab, which tries to ping the upstream gateway at my ISP. If the ping fails, it toggles a bit on the parallel (printer) port, the output of which is directly wired again to another of those $5 solid-state relay modules, which in turn is directly wired into the power leads of the modem's PSU. I installed this in late December, and the connection here has been SO MUCH more reliable than before!

Every now and then I think about making up a box with AC outlets, 8 solid state relays, and a single control cable with a DB-25 connector on the end for plugging into the server. I could then plug into this the various other computers and networking gear in the vicinity, allowing me to remotely fire-up an offline server (or an Empeg!) from a remote location on demand.

Someday..