Well-designed　2D　materials　with　ultrathin　structures　show　great　potential　for　humidity-sensing　performance　owing　to　their　high　surface-volume　ratio　and　a　great　number　of　exposed　atoms　on　the　surface.　However,　some　sensing　elements　employed　for　healthcare　applications　may　be　considered　as　potentially　risky,　such　as　inflammation,　granuloma　formation,　and　carcinogenesis.　Herein,　we　explored　biofriendly　humidity-sensing　characteristics　inspired　by　the　great　biocompatibility　and　conductivity　of　hyperbranched　polyethyleneimine-capped　gold　nanoparticles　and　cross-linked　with　polydopamine　from　the　adhesive　proteins　in　mussels.　It　was　successfully　employed　into　two　kinds　of　wearable　devices,　sports　watches　and　breathing　masks,　for　real-time　recording　humidity＇s　fluctuation　in　expiration　and　sweat　with　changes　of　individual＇s　crying,　laughing,　nervous,　sleeping,　training,　and　cold　states.　The　wearable　devices　allow　us　to　monitor　individual＇s　physical　activities　and　emotional　states　well,　suggesting　a　promising　prospect　in　safe,　reusable,　long　term,　and　noncontact　human　health　monitoring　applications.　©　2019　American　Chemical　Society.