Hopscotch is a visual programming environment, like Scratch or Blockly, that runs on an iPhone.
If your kids like to grab your phone and watch videos or play games on it, put Hopscotch on your phone and encourage them to make games instead of just playing them.
Here’s a piece from Wired that explains how it works (with some screen shots) and why it is so cool.
You might ask, why should my kids learn to code? And there are many great answers to that but I always like to answer that question by reminding people that instructing machines what to do is becoming an important life skill. And it will only get more important in the coming years. So getting your kids comfortable doing that at a young age is a great thing and Hopscotch is a great way to do that.