Interesting. I feel their is a lot of potential in a guardianship. Much like a mentor, a person has someone else they can connect with about how they are dealing with the situation. I do think it could be valuable to match people with others who have had some experience in the situation. Also a component of this could be the initial "campaign" of letting people know the site exists. Wonder if there are low-risk ways of getting the word out, maybe something like the street play concept (http://www.openideo.com/open/amnesty/concepting/street-plays-a-video-tool-kit-for-unlawful-detention/) from The Disrupters. This also reminds me a bit of http://www.patientslikeme.com/ connecting people with different health issues. The similarity lies in a balance of what information one would be willing to display publicly or privately as well as finding others with common ground.
Yes, I think if there was a way to have the detainees leave behind something visible from above or from a natural system within the city or village this could be a good idea. I am not sure such a high tech device is feasible for our situation given resources.