I picked up a new PSP Slim & Lite a couple weeks ago, and immediately fell in love with it. The screen's better, it's far lighter and best of all I can now play games using my TV as the display. Being a person with a physical disability 99% of my gaming is done at home, so this is a feature I really appreciate. Mainly, I appreciate it because I can finally share some really great gaming experiences with my wife and friends. Even though the output resolution is fairly low and the black borders around the game play are pretty huge, a simple hardware revision effectively turned the PSP into a home console. I can finally get people to help me with tough sections of games like Pursuit Force or Killzone: Liberation, or share an extended Jeanne D'Arc session with my wife who loves watching me play strategy RPGs. Not to mention the fact that the PSP also plays UMD movies. Since the format has essentially failed, it's been easy to find them dirt cheap at places like Wal-Mart (seriously, 2/$10). I had no idea that UMD discs were at the same resolution as DVD movies and thanks to the wonder that is h.264 encoding, a lot of times they actually look better.
I never though in a million years that Sony would be the first to offer such functionality in this generation of hardware, if at all. What surprised me even more was that you didn't need to have a PlayStation 3 to make it happen
Nintendo was giving gamers the option of playing their handheld titles on "the big screen" almost 15 years ago with the Super Game Boy attachment for the Super Nintendo Entertainment System, which not only allowed you to play Tetris and Metroid II on your TV, but could add colour to the games as well. Although it was not released, they also had a similar device for Nintendo 64. This is also the company that came up with the Transfer Pak, GBA connectivity (Animal Crossing, Zelda, Pokemon) and the device that's arguably keeping GameCubes hooked up and working, the Game Boy Player. This iteration not only played the current generation of handheld games from Nintendo's Game Boy Advance, but of it's predecessors as well. A function that the DS doesn't even have.
Even before Wii was released, I assumed Nintendo would have similar functionality between it and the DS thanks to the Wi-Fi capabilities of both systems. Here we are almost a year into Wii's life cycle, and still not a peep from them on a feature that a lot of people expected to be there. Nintendo could add such functionality to Wii using a firmware update, or extra channel that you could download, even though most people's Wii's 256MB of usable storage is filled with overpriced Virtual Console ROMs, but I digress...that's for another rant. Even if they went thier traditional route and released some kind of hardware adapter, I'd happily buy into it like a good sheep for the privilege of playing Advance Wars, Ouendan and Zelda on my TV and turning a usually solitary experience into one I can share with others.
The only thing I can see holding back such functionality is crossover sales. Would people buy Cooking Mama Wii if they can play Cooking Mama DS on thier TV? I know I wouldn't. At the same time though it may encourage companies, including Nintendo themselves to stop simply rehashing DS games for Wii and come up with some great new game ideas.