Here's my take on it, and mine alone. Do what you will, but I'm not responsible.
If the lipo goes off, there is nothing you can do to stop it. So, whether you are there or not is actually not going to matter much, unless you are there with the right kind of fire extinguisher in your hands. So, you might as well always charge in a fireproof container whether you are going to stand around and observe it or not. Just because you are there, don't assume you can charge without any fire protection, as they tend to move around shooting flames out, so anything flammable nearby is going to be messed up. So, no matter what, fire proof container unless you charge outside in the desert or something. The other thing is that the smoke is horrible and very corrosive. If it is in your house or garage, then you will suffer much smoke damage even if you are there with a fire extinguisher to put it out. You are better off making sure that you are able to charge safely if you are there or not. Especially since according the murphys law, the thing will only ignite when you are called inside to answer the phone or do something for the wife. You can sit around and charge all day, and the 1 minute you leave is when the fire will happen. So, you might as well secure your charging area pretty well, and not have anything in the area that you care too much about, except of course for the charger. I think that just like forest fires, STD's and teen pregnancy, the best bet is prevention. Make sure your cells are well taken care of. Know your charger, and never assume anything about the settings. I use a cellpro 4s, because I can't screw it up. I charge in a large clay flower pot, sitting on a clay base, and then I have a base from a larger flower pot to sit on top. It will contain fire very nicely. There's nothing I've seen yet to stop the smoke. What I would really like to do would be to build a small brick or cinder block bunker to charge in, so everything is protected from rain and all that, but no smoke or fire can possibly damage the house. or have a small fire proof enclosure in the garage than vents out to the outside by a fan with a duct, so no smoke can damage anything. That's an expensive and cumbersome way to go, and not likely to happen, unless I win the lottery and build a mega-house. Then I would have a workshop with one of those vent hoods for doing nasty chemical reactions in, like in chem class. Lots of ventilation. Sealed in cabinet with plexiglass windows, with the thick gloves mounted in them.
That's probably about the only thing that could ever truly be considered safe. Just having them in the house or car is a risk. However, life is not without risks. We are probably much more likely to slip in the tub and die than to ever experience a lipo fire firsthand.