I just finished my application for android devices, LifeTracking, which has been motivated by the discussions here; primarily discussions about akrasia and measuring/tracking your own actions. I don't want to make this sound like an advertisement (the application is completely free anyway), but I would really really like to get feedback from you and hear your comments, criticism, and suggestions. If there are enough LessWrong-specific feature requests, I will make a separate application just for that.
Here is a brief description of the app:
LifeTracking application allows you to track any value (like your weight or your lesswrong karma), as well as any time-consuming activities (like sleeping, working, reading Harry Potter fanfic, etc). You can see the data visually, edit it, and analyze it.
The goal of the application is to help you know yourself and your schedule better. Hopefully, when you graph various aspects of your life side-by-side you will come to a better understanding of yourself. Also, this way you will not have to rely on your faulty memory to remember all that data.
Edit: LifeTracking website
And while we are on topic of mobile apps, what other applications would you like to see made? (For example, another useful application would be "your personal prediction tracker", where you enter various short-term predictions, your confidence interval, and then enter the actual result. You can classify each prediction and then see if you are over- or under-confident in certain areas. (I remember seeing a website that does something similar, but can't find it now.))