What purpose does this serve? How do I do it? Do I need my USB cable or something? Most importantly, is there even a slim chance that my custom firmware will mess up the PS3 in ANY WAY?

I did try to connect my psp to a ps3 once... but it wouldnt allow me to, my firmware wasn't high enough but i doubt that it wouldnt connect just becuase you have custom firmware

purpose (forgot to write ): the purpose of diong this is i think that you can veiw whatever is on the ps3 on the psp (not sure) and you can use the psp as a controller (not sure about his either because of the right analogue stick, L3, R3, L2, R2

only thing i found out it could do is u could play music and movie from the ps3 onto the psp...

not much is used u basic can transfer music and videos and reciently the game Lair can be remote played so i guess it could be a future hope