Arrested?

I almost got arrested in my own home today, and I wasn't even doing anything illegal! Here's the run down of my day.

9:00am Try to set the house alarm before leaving. House alarm won't let me set it. 'I'll return home in an hour to set it.'
10:30am Stop by house on way to office. Set alarm.
10:43am Pull into parking lot at work. Cell phone rings.

Kind lady on the other line: "The motion sensor in your living room has detected motion and your alarm has gone off. We tried the house phone, and Gina's cell phone, you are the next on the list. We will send a guard to your house."
Me: "Do I need to go home?"
Kind lady: No. We will call you if there is a problem.

10:44:30am My thoughts: If the living room motion detector went off 5 minutes after I left the house, and no door alarm went off, that likely means the intruder was in the house the same time i was....
Now I am freaked out!
10:45am Try to call roommate. No answer. Gut feeling says go home and figure it out.
10:50am Leave office with secretary because I know I shouldn't go home alone (safety first).
11:00am Arrive at my house. Alarm goes off again. I check the house and call the alarm company to figure out what is going on.
11:15am My roommate comes home to get something (no idea what is going on because she has not checked her messages) and finds our house surrounded by 4 police officers ready to draw their guns and catch the 'house burglar'. Gina enters the house to find me on the phone with the alarm company. She verifies to the police officers I live there, they search the house and leave.
12:30pm Gina calls me and says the alarm has gone off again.
12:45pm Arrive home to help figure the problem out. Alarm company states our motion detector battery needs to be replaced....ummmm?????
1:15pm Battery is replaced and alarm does not go off again......

Shouldn't there be a better way to let a person know they need to replace the battery in the motion detector? Like the annoying beep that occurs in your smoke detector? It should not require 4 police officers to surround my house, almost arrest me as the intruder, and scare the snot out of me because the alarm goes off 5 minutes after I leave the house.