You will probably claim it's not "real" perfect pitch, but many people use their tinnitus to help them. They identified their ring as having, for example, F#, and suddenly their relative pitch became absolute.
Also your teeth don't change too much in adulthood save for cavities and the like, so if you hum, they'll resonate in a rather stable frequency.
Now there's a hack in the most delightful sense of the word
I've seen nothing to convince me that "absolute pitch" is anything other than relative pitch with excellent recall or persistent observation of pitch.