PSP Power Saver turns off the UMD driver when you are not using it. This should save you about 5% of your battery power.

Changes:

-Converted it to a prx because running the eboot everytime at power up was really bad
-Now 10%

http://forums.qj.net/psp-development-forum/151321-psp-power-saver-v-0-0-7-a.html