speaker, hidden inside the pillow. Messages are played when the listener presses the button embedded into the photo frame. The intended use case is that people record and send messages during the day to be listened to just before their partner goes to sleep.
However, there is no technical barrier in the implementation preventing participants from developing their own usage pattern.
Reference: Gooch, D., Watts, L. 2012 sleepyWhispers: sharing goodnights within distant relationships. In UIST Adjunct Proceedings '12 Adjunct proceedings of the 25th annual ACM symposium on User interface software and technology Pages 61-62.
http://danielgooch.synology.me/lddr.html
