The people who lived in this house before us replaced the batteries on their smoke detectors all at the same time (or maybe installed them at about the same time).  Which has been my bane for the last couple weeks.  Why?  Because throughout the last couple weeks smoke detectors have been beeping for battery replacements.  The smoke detectors are all about 10-12 feet away from one another [in different rooms] so it was hard to figure out why a freshly replaced batter was already dead.
Until I realized that the piercing sound that made my ears hurt was coming from a slightly different location.  I am totally going to do this to the next home owners because its kind of funny in a super-weird sort of way.