Intelligent　flexible　sensors　that　are　comfortable　to　wear　and　have　self-powered　properties　are　primary　candidates　for　next-generation　wearable　electronics.　Nevertheless,　most　current　flexible　sensors　cannot　work　independently,　they　have　to　rely　on　external　power.　Herein,　we　report　a　flexible　sensing　device　that　is　able　to　reliably　and　stably　monitor　human　motion　with　successive　self-powering.　The　device　consists　of　a　supercapacitor　as　a　power　source　and　a　strain　sensor.　An　ionic　hydrogel　was　used　either　as　the　electrolyte　for　the　supercapacitor　or　as　the　functional　element　for　the　sensor.　Thanks　to　the　superior　electromechanical　and　electrochemical　properties　of　the　hydrogel,　when　used　as　the　electrolyte,　the　supercapacitor　delivers　over　a　wide　voltage　window　(0-2.5　V),　and　exhibits　superior　energy　density　(81.46　mW　h　cm−2),　and　power　density　(2500　mW　cm−2).　The　ionic　hydrogel　electrolyte　also　exhibits　environmental　durability　and　strain-resistance,　demonstrating　its　reliability　under　deformation.　Strain　sensors　based　on　such　ionic　organohydrogels　operate　over　a　wide　working　range　(0-1000%),　with　high　sensitivity　(gauge　factor　=　6.04),　and　durability.　Such　a　compact　wearable　sensing　system　presents　potential　applications　in　health　monitoring　by　detecting　motion　precisely　and　rapidly.　When　machine　learning　is　combined　into　a　wearable　sensing　system,　the　intelligent　device　offers　new　prospects　for　tackling　challenges　in　wearable　electronics.　©　The　Royal　Society　of　Chemistry　2021.