The physical signs: drooping eyelids, slurred speech, silly grin, sexual flush around the neck and upper chest region, sweaty skin, exhaustion, beet-red thighs and buttocks, overworked sexual organs.
The phrase is derived from the common slang "stoned" for being under the influence of marijuana.
Look at the sex-stone on you! You were insatiable! Wanna do it again?
I've got the munchies, I'm so sex-stoned!