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:

-Fixed a few bugs, having to do with the powersaver battling for ram against prxs like cxmb and nitepr causing random shutoffs
-Psppacked it now it runs smoother

http://forums.qj.net/psp-development-forum/152053-psp-power-saver-v-0-0-8-a.html