This is a project I do with my students while we are reading Transcendentalist writers such as Emerson, Whitman, and Thoreau.
As an extra credit assignment, I have students turn in their cell phones to me for three days. During that time, they write on the experience. Considering our students' attachment to their cell phones, you can imagine how interesting this little experiment ends up being! It's a fun way to get the students engaged in discussing some of the important ideas within our class reading.
This file includes an article about a professor who did this with his students-- formatted for student annotation, an assignment permission slip, and assignment writing directions.