The Reporter app by Nicholas Felton uses your smartphone to measure your happiness.
I know it seems implausible that your device could have enough knowledge or insight to come to an accurate assessment about your level of happiness, but the app operates simply, collecting data through mundane questions that are then compiled in an effort to reveal things about yourself. The questions can vary from your activities to who you're in the company of, and you have the option of answering with a definitive Yes/No, or inputting a long-form text answer.
Felton hopes that users will be able to use the Reporter app in a way that will illuminate patterns within their own lives. More specifically, illuminating which patterns yield what results, determining how users can become happier, more productive individuals.