Quote:
Originally posted by timothy
yes, just be sure to take power BEFORE the fuse, and then add a fuse of your own 
No you dont want to do that You should tap it after the factory fuse. I have seen so many cars with burnt up factory wires by doing that and here's why. The back up fuse before the fuse box in the interior is the big 60A or 80A sometimes 100A by the battery. imagine if youre wire is shorted between the main fuse and the fuse you added. You're gonna have a fried wire from the fuse box to the battery. Beside The opus's acc wire takes only 150ma or .15amps. It's not going to add any more strain on the wire you tap it to. You should tap the wire after the factory fuse then add your own fuse. If you need any power larger than the factory wire can handle, you should go directly to the battery.
Rbarr to answer the "will any line that only receives power when ignition is on work as the IGN/SW line?" question is no. Some ign wires go to onboard computers or airbag system that you dont know about. or to the wiper. It works fine until it starts to rain. You should stick with radio, cig lighter or the clock. Since you got 2 cigeratte plugs on that panel you already took off, you can tap the acc wire there. white/black is ground on Toyotas, brown on the radio is ground too. as for ACC, Toyota change colors once in a while.