I just ran across this short little video on how to make a micro=home. I love this concept. The thing costs around $100 to build and would be a place for a homeless person to crash. Of course, I am sure there are building codes that would make this illegal, but slap some wheels on it and call it a wagon and you are probably good to go. The only remaining problem would be a place for them to put it. If they find some remote public land and aren't bothering anyone, I say leave them the heck alone.
I would also like to see something like this in airports. It would be awesome to be able to rent a few hours in something like this to crash while waiting for a connecting flight. I believe I have heard of such things in Japan, but I have never actually seen one.