This application by Akez flashes “own waves” to a PSP. Regarding the author it is fairly easy to use and it shouldnt brick your PSP unless the file you select to copy is not a system_plugin_bg.rco file.
Changes:
EDIT: I checked the upload that i put on megauploads and it looks like i hadnt included all the files. I have now added all the files and have added a check to see if the battery is lower than 5% and if it is, it wont change the wave. I have updated the link and checked it this time.