Even with a "smart charger" that is designed for Lithium chemistry batteries there is still a risk of fire. These batteries need to be observed as they are charged and they need to be charged in a fire safe container. I use a Lipo sack to charge my batteries in. This will contain any flames that may occur if the fire bursts and catches fire. As far as watching them?? that simply means you are present in the room while they charge. I charge them in my shop while I am working using the lipo sack sitting on a concrete block to contain them if they burst. Lipo's can be safely charged in an hour so it's not like Ni-mhs where you have to charge them overnight. If you live in an apartment building you could charge them on your balcony if you don't want to do it inside the house

The risk from Li-po's is real, but it is not common if you give the batteries proper care. However, they should be handled with care in the event that they do burst and catch fire. You don't want to burn down your apartment building if they are handled improperly. A few simple safety steps go a long way here

Ken