Very cool!  You can also order large magnetic signs and apply them to the wall.

I don't know about the paint, but do watch out for the magnets and kids.   Serious magnets can cause big problems for kids if swallowed.   From the pictures it looks like the magnets myaimistrue used wouldn't be swallowed, but my pediatrician did tell me she had a case where a child had swallowed some of the small marble-type magnets that come with toys.  Required surgery to get them out because they had clumped together and wouldn't pass.   

Great idea--I'm also thinking for a kid's room. However, are there any sort of health hazards associated with this kind of paint? Just curious.

Excellent idea for a kids room. The paint may be pricy, but it's cheaper than repairing walls after they've been damaged over and over by tacks, nails, or tape.

Love this, I might try it. Thanks!

cool idea. this might be cool on a door too