A Korean inventor, Seok Hong Jeong, has come up with a dual LCD mobile phone prototype. This is not your usual dual screen set up with one of the displays simply displaying information like caller ID. This is a phone with two relatively large screens. Normally, you have just one screen showing but a second screen can be extended from underneath the first so that the two screens are side by side. Double the screen real estate almost instantaneously!
Jeong has already applied for patents for his invention.
Meanwhile, Mitsubishi also unveiled a different two screen mobile phone prototype at the Hong Kong ITU World tradeshow. This design features a touch screen on each half of its clamshell design (one replacing the keypad). Rather than intending to increase screen real estate, Mitsubishi is looking at using the second screen to improve the user interface.
Sources: Engadget and PDA France