We have been given the project idea to build a rescue bot that will find a victim trapped in some sort of debris . It is assumed that the victim will have some sort of transmitter ,either RF or ultrasonic.The bot must sense the transmitted signal and find the victim,avoiding obstacles in its path. We are planning to do the obstacle avoidance using ultrasonic sensor. But we are at a dead end on detecting the victim. Which would be better - ultrasonic or RF ? pls help us.thanks in advance for any ideas,suggestions and circuits.