Expert answer: Gwenn O'Keeffe, pediatrician and author
No, it's not safe.
First of all, phones are covered in germs. In swab tests, cell phones have more germs on them than most everyday items.
Cell phones also have all sorts of parts. Older phones have buttons that could be a choking hazard if they came off. Pieces of phones can break off, and the jagged edges could cut a baby's mouth or scratch his or her eyes.
If a cell phone breaks open, the inside has small pieces that are choking hazards and can also cut a child. Some pieces of a cell phone, like a battery, microchip, or circuit board, are 911 moments if swallowed.
Beneath the colorful display screens of newer phones, like the iPhone, are unsafe chemicals. If a child whacks the phone and breaks the display, he or she could be at risk.
Once your child is past the phase of mouthing everything he or she grabs, letting him or her play with a phone is safe, if germy. But I do recommend being judicious about how much you use a phone as entertainment for your child.