2007 prius ready state wire needed

I own a 2007 Prius, North American Model. (Rest of the world, the car is SLIGHTLY different, so I point this out)

I just bought a beautiful 2000W power inverter which I intend to connect directly to the 12V battery.  The problem is, if I leave it on, I will have a large doorstop.  (I would say paperweight, but that is a light automobile :) )

OK.  If I tap into the power outlet, I can control the inverter with the car's power button but, with my desire to be green, I will put my phone in the car and turn on the outlet to charge it.  This is not the final result I want.

Somewhere in that wiring nightmare, there is a wire I can tap to add a relay so the inverter only runs whenever the car is in "Ready State" and therefore supplies power going into the battery.  Its my understanding that a 2000W load will drain the poor thing in 15 minutes, then I will be limited to ~1200W as that is all the car will provide.  This inverter is overkill for my expected uses, but I got it at a GREAT price, and I can use it in the event of a blackout for my fridge.

If somebody can tell me what wire and where to find it, I would really appreciate it!

I take it that you are not really familure with a Prius.

There is no ignition wire, no starter motor.  I'm trying to find an equivelant.