We're going to build an Arduino reminder machine with an Arduino Uno, MaxBotix EZ1 sonar rangefinder, WAVE shield, and the DS1307 real-time clock. This builds on our previous project, How to Build an Arduino Pest Repeller on Linux. When you walk by the MaxBotix it will trigger the WAVE shield to play scheduled audio reminders. Or read poems, or play music, or anything you want. It also includes a timeout so it doesn't drive you crazy playing the same reminder over and over.