I can't see why you'd really want to do this, as the previous replys have pointed out...but;

You could possibly use the Remote Amp Turn On wire to drive a relay that switched the ignition line. You'd have to be sure that you could still get power to the accessory line though or your car would never start. You would also need to ensure that the empeg was protected against the reverse switch-off current generated by a relay (easy enough - and the empeg may already have internal protection.) But the big thing is this - if you turned off your empeg accidentally whilst driving, your car would stall. Is that desirable?