Smartphones - This can do a lot of things for moms - communication through call, text and email; documentation - taking photos, videos, make sound recording; and provide entertainment - music, games, etc.
Tablet PCs - They are just bigger versions of smartphones. They are more appropriate to use if you have a great deal of work to finish in between house chores and caring for the kids. When you are out with the kids, they can be a source of enjoyment if they are bored waiting for you.
Kindle - So the kids already got your tablet to play games. If you have got a Kindle, you can fight boredom and let time pass by reading your favorite book beside your kids.
