Use the power of your phone to destroy shiny police cars! Switch over traffic lights and cause a big pile up! Stalk the funny-looking NPC with the hair and find out their life story!
On paper, it all sounds like refreshing, unique fun. But the hacking concepts of Watch Dogs have to be in-depth, detailed, varied and have loads of different possibilities for this game to succeed. It has to let you use hacking how you wish, and not lock you out from things that should be hackable but just aren't.
If hacking isn't fun, time consuming and only has scripted effects, part of the appeal of Watch Dogs instantly disappears along with it. This should be a hacker's playground, not a hacker's cage, and as creepy as following people around and making their toaster betray them at hilarious moments would be, it would still be entertaining.