For the last three days I've been using Weightbot to record my weight. Weightbot does a few simple tasks in an elegant and easy-to-use interface that makes me want to record my weight on a daily basis. First, it records your weight. Two taps, and you're done. Second, and even more importantly, it asks you for your current height and goal weight. This provides Weightbot with the information it needs to provide you with your BMI (Body Mass Index) and with an easy-to-read graph to show your progress against your goal.
Oh, and I'm back on the diet. I'll be posting screenshots of my own progress once I get at least 14 days worth of data recorded into Weightbot. At which time I'll be sharing my method for weight-loss this time around as well.
If you have an iPhone and want to track your weight; get Weightbot.
Source: Weightbot by Tapbots.
Additional resources: How to calculate your own BMI.