Don't you just hate it when you go to the movies and someone's phone goes off? Even if they don't answer it and chat away for fifteen minutes of your movie, it still just killed the atmosphere. If you've ever wanted to ensure your movie-going experience remains undisturbed, you might want to check this out.
Apparently you can pick up a cell phone jammer for less than $50. Is there a catch? Of course. The first one is that it doesn't actually work with US frequencies. However, with some knowhow, you can fine-tune it to block out signals used here in the states.
The second catch is that here in the US it's illegal to use such a device to block these signals. It's still a pretty cool project, just be warned that there are consequences for actually using one.
Modifying a cheap portable cellphone jammer [via make]