Google "Battery University lithium safey" if you haven't read a lot about this stuff already. I suspect that that concerns over protected Li-ion cells are probably a bit of a red herring, especially if you are using Li-pos anywhere already or are using cheapie chargers.

What devices do you have that require loose Li-ion cells anyway? There really don't seem to be that many consumer uses for them outside of flashlights.

If you really want safe, you might be able to get away with a bunch of NiMH cells, but again that really depends on application.