Nintendo has said that it's "keeping a close eye" on the infamous Nintendo DS R4 device.

R4, which is sold openly in Japan's Akihabara district and online to consumers around the world, allows users to load MP3s and applications onto flash memory and play them back on the DS.

But the real point of concern for Nintendo is that it also allows people to run ROMs of DS games, enabling piracy.

The R4's been around for months, along with other similar devices like DS-Xtreme, but in a piece by The Times in the UK a Nintendo spokesperson offered this comment:

"We are keeping a close eye on the products and studying them. But we cannot smash all of them."

A spokesperson told Eurogamer this morning that the platform holder had nothing to add, and wouldn't comment on the legitimate uses for the device.

Proponents of the R4 claim that there's nothing wrong loading "backups" of ROMs for games already owned or engaging in the homebrew development scene - similar to the equivalent for Sony's PSP, which has a longer history of underground developments thanks to its more approachable Memory Stick format.

So yes, it's one of those situations where the device itself isn't illegal, but some of the things it enables are. Napster all over again.