sounds very do-able. the gen 5.5 camry's have this feature^
Re-wire all the exterior lights with a time. The ext. lights have a constant power source even w/ ignition off. So just tap into that, but you'll be leaving your light control stalk always in the on position unless you bypass it somehow. You will have to delete the drivers door switch that turns the lights off when the door pops, and probably remove the twilight sensor on the dashboard if you have the light sensor feature.
It seems easier to do something like this w/ just the FOGLIGHTS, less wiring, no worries about altering controls and the door switch. But I do not have any wiring diagrams to assist you, but i always wanted to do it.
If you can figure the wiring out please share

thanks
EDIT: ^yeah an alarm sys will do that, but nothing compares to figuring it out D.I.Y. style.