Example 1: One night I was going to a Roots concert and I went through the venue's website on my Google Chrome on my laptop. Then, right around concert time, Google Now alerted me to what subway I should take to get there.
Example 2: I searched for the Phillies score once on my tablet, and now my phone tells me about the score of each game. Again, I never asked.
Example 3: After 2 days, Google Now guessed where I lived/worked and what time I left for work most days. I don't use any check-in services or anything like that it really just guessed. Then it started telling me what time I'd have to leave home/work to get there on time based on the current subway schedule. Exactly what I wanted, never asked.