Darkwolf released today an app that can make the PSP a sensor bar for the Wii, from what I can understand. It has not been tested yet, so Darkwolf can't guarantee it works, so please, if anyone has a Wii, can you test it and post results? Thanks.
This is from PSBs readme file:
simply load psb from xmb, plce your psp on top of, or under your TV and point
the ir port located at the top of your psp facing your holding your wiimote.
THIS APP IS DESIGNED TO ENCOURAGE PSP-Wii FRIENDLYNESS
this has not been tested with a wii console and is currently only a proof of concept basic design.
may work better with 2 psp's scince there is only one IR led on each psp.
anyhow this may not work with only one psp and the more the merrier.