Did you get a "Permission denied on /dev/i2c/0" message?
If so, it's because it has to be run by root by default. Solutions: be root user, use 'sudo' (prefered) or chmod a+rw /dev/i2c/0 (note: makes the device writable by anyone - not prefered).
Never do the rocketeer's second solution.. instead su - to root, then type chmod +s /bin/xboxtemp. Infact.. ill make the patcher do this automatically.