Here's an idea that's been tried before, but the Nimzy Vibro Blaster is the smallest device yet that attempts to turn any flat surface into a loudspeaker. Stick the sucker onto a window, wall, anything flat, and then the Vibro Blaster supposedly rocks the object into musical nirvana.
Its manufacturer says its frequency response is 220-10,000 Hz, which is not exactly high fidelity, but might sound good enough to listen to talk radio. That said, it might be a costly experiment at $132.
Nimzy Vibro Blaster turns flat surface into speaker [TechDigest]