My 4 year old has a tablet, and I'm getting her a smart phone as soon as she can figure out how to text. She uses it to watch shows, draw, play games, facetime with her grandparents, look at family photos, etc.

Most of the "harms" of screen time disappear when adjusted for things like socio-economic status: http://fivethirtyeight.com/features/screen-time-for-kids-is-... http://daily.jstor.org/screentime-feminist-issue. Basically, like most parenting advice, exhortations to limit kids' access to screens is based on pseudo-science and old wives' tales. It should not be taken seriously.