Tlhere have been a few documentaries on lately about children who swallowed button batteries (like the ones in a TV remote) and one who swallowed magnetic balls. The result looks at first like a virus, with fever and no appetite. One set of parents did not accept this, and demanded an x-ray, which immediately detected a button battery.
One little boy had swallowed several magnetic balls off a desk toy, and they joined up in his tummy into a deadly row which started to destroy his internal organs.
If a hospital catches this in time, the children can be saved, but those things are lethal, absolutely lethal, and can cause irreversible damage. Just a warning to be very careful about batteries and magnetic small objects if any children are around.
What happens in a lot of cases is that the toddler picks up the TV remote, drops it, the back pops off and the battery falls out. The toddler then picks up the battery and eats it. In America one program said there were over 2,000 cases like this each year!
The advice given was to duct tape your remote, so that it won't be dropped, the back come off, and the button battery roll across the floor where a child can pick it up and swallow it.