First for me is my Withings graph (past 18 months shown.) To anyone looking to either gain or lose weight you pretty much need a scale and I love that the Withings scale syncs over wi-fi and allows you to view the results on iOS.
Second is my Lift streaks for exercise and eating well. When I cheat I know how long its been since last I cheated. It's awesome reinforcement.
What works for you?