TJM Innovations has introduced its new Bandshell case for the iPhone 3G and iPhone 3GS. The Bandshell claims to improve the sound coming from the iPhone’s built-in speaker via a “sound door” that slides out from the rear of the case to enhance the speaker’s acoustics. Other features include a flat side that enables the iPhone to stand on its own, and open access to all ports and controls. The Bandshell for iPhone 3G and iPhone…