Then why can shinigami and hollows sense their presenceFullbringers don't have reiatsu. It's something else.
The only person who i think does not hav reiatsu is inoue even Aizen said he abilities transcend that of a god 0_0 (i wouldn't think so due to her being unable to protect her self all the time and is really annoying and dumb in the manga some times remember one of the chapters a few months back "Why me sad"-_-)