Here's the official description of the movie:
Imagine every cell phone, radio, and television in your city suddenly broadcasting the same mysterious signal over and over. Now imagine these "terminus" transmissions evoking violent, uncontrollable, psychotic chaos from everyone who comes in contact with them.
It's a pretty cool concept and well executed (no pun intended) in the movie.
I'll give you a couple of minutes to watch the trailer before I go any further...
The version I saw was unrated (they don't give MPAA ratings to the films at the Sundance Film Festival) so I don't know if the theatrical release will have any cuts from the version I saw. Although it's extremely violent and bloody, I'm guessing it'll survive an R-rating without any edits.
It's certainly not for the squeamish, but if you like horror and comedy mixed together I think you'll like it. Hopefully it'll get a much wider release than the recent zombie comedy Fido, which certainly deserved better.
You can watch larger versions of the trailer over at Apple.com.
The Signal opens on February 22nd, 2008.