Nine hours, Nine persons, Nine doors

EDIT December 2010 the game is now out in English:
9 Hours, 9 Persons, 9 Doors

If you've already played it and are looking for other games like this, search for Ever 17 (same author) or Fatal Hearts (same gameplay).

Original post follows:

Japanese-only for the moment, but an interesting novel/adventure game for the DS.

Play novel horror puzzle game developed by Chunsoft and published by Spike for Nintendo DS in Japan.
Nine People have been kidnapped, each person has a bracelet/watch numbered 1-9 alongside 9 doors and 9 hours in which to escape. To enter the required door the people need to team up to match the number on the door i.e to open door number 4 needs to be bracelet number 1+3 to enter together, causing people to split up and explore different areas. Once inside said door you are locked in and required to finish a puzzle in order to leave.

source

The official site is here but japanese-only. They also seem to have a free webgame/preview/demo related to it.

Game can be purchased here. No idea if it'll ever see translation.