van der broook

Hi Let me start off by saying, that I am a complete noob when it comes to electronics. I am a software developer by day and geek by night, but electronics is not my field by any means. I hope I am on topic here, as I found the forum by googling for forums about RFID. My stepdaughter has a very severe degree of autism, and is unable to take care of herself. On several occasions, she has managed to run away from us or her schools/institutions, and it has taken us up to 3 hours of intense search + police help to locate her again. All kinds of bad things can happen to her while she is gone. I want to be able to track her easily, if she runs away. Now here is my idea - it might be utterly useless or impossible - but it will get you an idea about, what I am looking to achieve. I am thinking, we give her a bracelet with some kind of transmitter (RFID?) that has a range of at least 3-400m, that she cannot take of (that means waterproof is a must). Then as soon as we find out, that she has run away, we get out a receiver/tracker of some sort - and we would be able to cover the entire area she might be in within 20 minutes in a car. As soon as we pick up her signal, we should then be able to pinpoint her location by some sort of directional tracking (not sure if that is the correct term). Is something like that possible? What would it require? Am I overlooking a much better idea? Real time gps tracking would be perfect, but I think the issues of battery life + size rules that out. Am I wrong? I hope for your assistance and advice. Thanks in advance Klaus