Looking at your smart phone may in fact be more interesting than watching your small child, at the margin at least. It seems that some child injuries may be going up for this reason. Here is a new paper (pdf) by Craig Palsson at Yale:
From 2005 to 2012, injuries to children under five increased by 10%. Using the expansion of ATT’s 3G network, I find that smartphone adoption has a causal impact on child injuries. This effect is strongest amongst children ages 0-5, but not children ages 6-10, and in activities where parental supervision matters. I put this forward as indirect evidence that this increase is due to parents being distracted while supervising.
Here is Palsson’s other work, I hope he sends me a copy of his Haiti research once it is available.