3 links have been added on this idea.
  1. Make sure they know its not real. If they are old enough they will think its a mean trick. as it reminded me of this prank.

  2. Good idea, though I can only find ones with stickers on the front rather than a working simple display. Here is an example, why not make it work, people would pay a few bucks for one for a toddler it if it bleeped.

  3. or make a cover and app that turns your old iPhone into a harmless child’s toy? Read this, great idea imho.