There are spies everywhere. With RFID tags, and now Cokes with GPS devices and
built-in cellphones.

Read on:

NEW YORK - There's a new security threat at some of the nation's military bases
- and it looks uncannily like a can of Coke. Specially rigged Coke cans, part
of a summer promotion, contain cell phones and global positioning chips. That
has officials at some installations worried the cans could be used to
eavesdrop, and they are instituting protective measures.

Coca-Cola Co. says such concerns are nothing but fizz.

Job done!

http://www.phonejammer.com/

Similar (but larger) units are available around the world. I explored importing
them for sale to hospitals, cinemas, concert halls, etc., but was notified by
FCC they're not legal.

The FCC did admit in a phone call that a "passive" device (lead lined walls,
screened rooms) might ALSO be illegal.

Interesting thought.