In the attack described here: http://media.hacking-lab.com/scs3/scs3_pdf/SCS3_2011_Capkun.pdf http://media.hacking-lab.com/scs3/scs3_pdf/SCS3_2011_Capkun....

In the attack described here: http://media.hacking-lab.com/scs3/scs3_pdf/SCS3_2011_Capkun.pdf http://media.hacking-lab.com/scs3/scs3_pdf/SCS3_2011_Capkun.... the attacker has two devices communicating by radio. Device A is near the keyfob, and device B is near the car. Each is a repeater for the other: Whatever the car sends is picked up by device B and repeated by device A. Then the keyfob's response is picked up by device A and repeated by device B. This type of setup will defeat both of your proposals. Triangulation won't detect anything out of the ordinary, because device B can be right next to the car. And the ultrasonic challenge/response can be defeated just like a radio challenge/response, using microphones and speakers on the repeaters.