Check out Live Happy, a positive psychology iPhone application developed by Signal Patterns Labs (the same company that developed the Gratitude Stream iPhone app). The application is based on the research of Sonja Lyubomirsky, a psychologist at the University of California, Riverside, and the author of The How of Happiness. Grab the free version of the app or the paid version, which allows you to send Lyubomirsky questions.
Live Happy prompts users to perform activities (right on the iPhone) that research has shown help to boost happiness. These include things like taking a photo (to savor a moment), texting a thank-you message to a friend, or performing a random act of kindness.
Could these kinds of one-offs actually make people happier? "As a whole," says Lyubomirsky, "performing these activities adds up to a new mindset and a more positive way of engaging and viewing one's daily life."