Ground-Shaking Police Cars

It seems that ever since the Nintendo 64 rumble pack came out, all kinds of gadgets have been adding the vibrate-to-get-attention function as a way to silently grab someone’s attention. From cell phones to children’s toys, this tactile form of feedback is a very effective way to capture someone’s focus when sound is either inappropriate or ineffective.
This particular product uses ground-facing sub woofers on police patrol cars to shake the ground and alert people to get the heck out of the way. In today’s age of crowded streets and loud car stereos (which also shake the ground, but that’s another gripe altogether), this is a great way to get attention in a somewhat discrete way.
I predict that more and more gadgets will add vibrate functions to grab our attention- wouldn’t it be nice if your radar detector shook your steering wheel instead of blaring its awful alarm sounds?
http://www.engadget.com/2007/11/21/police-rumbler-grabs-your-attention -rattles-your-teeth/