Japanese designer Kouichi Okamoto is looking to shake up the page-holder game with Bookmark Light. It's a regular bookmark by day, but doubles as a reading light at night. You'll need a lithium coin battery, though.
The shift from bookmark to nightlight is made by placing said battery into a slot and folding the film-material bookmark over. It works by using a silver conducting and a special type of nanoparticle ink that conducts electricity.
The Bookmark Light is currently available from the Kyohei Works website and is selling for ¥ 2,128, including shipping (roughly $20, AU25, £15).