Sorontar was wondering last week if the memory matching game could be implemented in redstone. Here's a world download where I've made a small version. There are only 4 items, so 2 matches. You can see, the redstone circuits get large quickly, but the principal here could be extended to larger sets. I'd post a video, but I don't have software that will record Minecraft.
The world was created in 1.4.