SuccessHK have on their site (cool stuff section) a new handheld console, that plays retro games that come in cartridges of up to 25 games on 1 cartridge, heres more info:



The 2.5'' crystal display adapting the most advanced Low-Temperaure Poly Silicon technology which provide the user with 960x240 high-resolution color images. The user-friendly multimedia platform support Play-On-TV function. Plug it on TV for clearer and wider images*. Simple but streamlined product design will make your hands stuck on it. It only weight 75 grams. Strict manufacturing procedure guarantees higher reliability and safety.
*Not all cartridges have this feature. NTSC/PAL cabe selected in particular cartridges setup
3 AAA batteries are required(Not included)
Cartridge is not included

The console sells for $35 and the game cartridges are $8 for the 8 bit games and $10 for the 16 bit ones.

Not a PSP rival but for retro fans it may be worth a looky.