"Developer Jeff Sharkey has come up with an Android hack for
OLED display phones (Nexus One, Incredible, etc) that he claims
almost doubles battery life: go into "night vision" mode by
filtering "separate pixel elements for each color channel" so that
only one color shows at a time (red works best).
"First of all, it's worth noting that he did this hack in
airplane mode with GPS off, though it doesn't seem that that is
necessary for the hack to work. As Sharkey puts it:
"Filtering to show only red pixels only requires 35% of the
original baseline OLED panel current, on average."