Rumble Pack for DS?

I was reading hands-on impression of Metroid Pinball for DS, and people are saying that some of the demo units had a rumble feature in it, coming from a GBA cart.

here’s is a quote from PlanetGameCube

One major surprise is that some copies of Metroid Prime Pinball on the show floor featured rumble capability. Yes, rumble as in force feedback like Pokemon Pinball. This obviously couldn’t be built into the tiny DS packs, so I had a look underneath the DS playing the game and it had a GBA cartridge plugged in as well. I figured that the GBA cartridge was the one doing the rumbling, and this was later confirmed by PGC chum Chris Kohler. Apparently Chris saw someone booting up a DS with Metroid Prime Pinball in it, and the initial selection screen said that there was a “GBA Option Pak” in the GBA cartridge slot. I’m not sure whether or not Nintendo will sell this standalone Rumble Pak for use with rumble-enabled games, but it definitely exists. Hopefully it will be a pack-in when Metroid Prime Pinball is released, because it works like a charm.

This could be interesting if more game uses it after that. But i wonder how it will affect the battery life.

source: PlanetGameCube