The TurboExpress or PC Engine GT (Game Tank) in Japan was a portable version of the TurboGrafx-16/PC Engine (video game console), released by NEC in 1990 for $249.99 (the price was briefly raised to $299.99, soon dropped back to $249.99, and by 1992 it was $199.99).
It was the most advanced handheld of its time and could play all the TurboGrafx-16's games (which were on a small, credit-card sized media called HuCards). It had a 66 mm (2.6 in.) screen, the same as the original Game Boy, and could display 64 sprites at once, 16 per scanline, in up to 481 colors from a palette of 512. It had 8 kilobytes of RAM. The Turbo ran its 6820 CPU at 1.79 or 7.16 MHz.
The optional TurboVision TV tuner included RCA audio/video input, allowing the player to use TurboExpress as a video monitor. The TurboLink allowed two-player play. Falcon, a flight simulator, included a "head-to-head" dogfight mode that could only be accessed via TurboLink. However, very few TG-16 games offered co-op play modes especially designed with the TurboExpress in mind. As of July 30, 2007, the TurboExpress has sold 1.5 million units.
Source: Wikipedia, "TurboExpress", available under the CC-BY-SA License.