Years ago... mid to late 90s... I had everything X-10'ed up in my house. What I didn't know is that my house alarm was also X-10 capable.
One night, I couldn't enter the code in time and you could see what house was alarming for miles around. Inside and outside the house, everything that could blink was blinking - to go along with the blaring sound.
I cancelled the alarm service (and kept the alarm) soon after because 1) it would freak anybody breaking into my house out, and 2) if the cops couldn't figure out that there was something going on at my house without somebody having to call them, they just weren't doing their job.