The Letter is a film showing at the London Film Festival which seems to be both about text messaging and to employ text messages as a narrative device. You can find details of time and venue in the above link. The festival website describes the plot: "A schoolkid splits from his classmates and heads home for the evening. Around 9pm, feeling ‘somehow lonely’, he sends a neutral text-message to a friend. From this point, The Letter shows nothing but the boy’s phone, either sitting in its recharger or brought into close-up so that we can read incoming messages and watch the writing (sometimes rewriting) of messages to be sent." Nice.
-kris