Well nothing will really keep kids out but this makes me feel better.
This is simply a speaker magnet placed in front of the blade cover. Because it is in front there is no way to touch the blades.
Speaker magnets are very strong (cast iron table helps). The one in the picture is from a 3 inch speaker cone and I cannot lift it off the table. To remove it I either pry it off with a screw driver or slide it off the edge of the table.