Vote With Me matches your phone contacts with an excellent voter file and can show you who you need to turn out in any given election. Given the biggest problem in any election isn't registration, but just getting registered voters out to the polls, this is a crucial tool. It's also much better to get a message from a friend vs. a campaign. The crowdsourcing of who's been contacted through Vote With Me is also a great touch.
As someone who built this in 2011, but using Facebook friends, I know it's a great a tool, but it's up to passionate folks to use it and turn out their friends, it won't use itself. Get going.
Would like to know how the app handles the data it gets access to?
It's a great way to see who in your friend sphere might be in a critical campaign and then gently nudge them (with your explicit permission) to vote. Yay!