You could have sudo not ever require a password for a certain command with an entry in /etc/sudoers:
Or for the setuid route, it looks like in Leopard setting the setuid bit isn't enough any more -- the code also has to call setuid(), which is the way it should be, I believe. So for example:
mikuro ALL= NOPASSWD: /path/to/command
Try that with the setuid bit set and it should do what you want.
if (setuid(0) < 0)
fprintf(stderr, "setuid() failed\n");
I'll spare you the usual security warnings and all that...