From the same hacker that made the GB emu for the PSP. It's not released till now, but watch his download page for when it's out: http://mirakichi.hp.infoseek.co.jp/software/RIN.html
The GB emu is in a new version as well, now with rom selector and double screen size option.
Fredi
PS: Everything still only for jap. PSP with firmware 1.0 of course.