i posted this on audiworld earlier and here before as well
Use a relay to get power switched by the RNSe amp remote on signal (i think connector d pin 13)...this way if car is not on but radio is phone works...ALSO if turn off car and radio turns off phone stays on b/c radio does not immediately shut off remote on signal - this alone is worth it.
besides you can now hook up many devices to be switched by radio irrelevent of car on/off such as dvd player, etc.