Exhibit A - the most recent and relevant one first:

PS Vita is launching with backwards compatibility in a tougher mobile space, with digital-only backwards compatibility (given today's announcement that the UMD transfer program is not coming to America).  Check out my mockup of the PSP Too, and external UMD Drive that will never happen, that would have allowed Sony fans to play all their PSP games, giving them experiences to enjoy in higher fidelity on the Vita's OLED screen and dual-analog control scheme.  This would bridge their launch while adopters saved their bucks to buy Vita software:

PSVita and PSP Too

Read an article of mine about the alternate reality Sony which would have decided to release such a peripheral here.

Exhibit B - Less recent, less relevant, and really more of a flight-of-fancy

3DS had a rough launch, and when it was first devised and announced I had little excitement for the unit.  Honestly, even with the recent software bump, I still don't.  3D as a new level of electronics revenue has been a failure, and no amount of insistence is going to make the feature any more attractive.  Recent additions like the Circle Pad Pro have highlighted the fact that the system itself has control limitations when it comes to the types of games that gamers want, that really push the hardware.  Ironically Nintendo is learning what Sony already did with its PSP:  console-quality experiences not only work better with two sticks, but work better on a console and through a television set.  That said, it has been since Sega Nomad that any manufacturer has tried to offer the value of a console experience becoming portable with the very same software a consumer has already purchased.  As 3DS approached its launch, I surmised just such a device from Nintendo as the ultimate PSP and Vita killer:

Gameboy Cubed

Read an article of mine about the alternate reality in which Nintendo would have decided to release such a system.

Certainly Nintendo, more than Sony, deserves more credit in using backwards compatibility to bridge DS owners to the 3DS, making my second example perhaps more of an example of wishful thinking than my first.

But with software priced 4000% higher than many games on iOS, further effort in leveraging existing software libraries could have been a powerful method to offset the devaluation of software from their one, true competing platforms.

I hope you like the mockups, and the linked articles.