The　Internet　of　Things　(IoT)　combines　various　sensors　and　the　internet　to　form　an　expanded　network,　realizing　the　interconnection　between　human　beings　and　machines　anytime　and　anywhere.　Nevertheless,　the　problem　of　energy　supply　limits　the　large-scale　implementation　of　the　IoT.　Fortunately,　thermoelectric　generators　(TEGs),　which　can　directly　convert　thermal　gradients　into　electricity,　have　attracted　extensive　attention　in　the　IoT　field　due　to　their　unique　benefits,　such　as　small　sizes,　long　maintenance　cycles,　high　stability,　and　no　noise.　Therefore,　it　is　vital　to　integrate　the　significantly　advanced　research　on　TEGs　into　IoT.　In　this　review,　we　first　outline　the　basic　principle　of　the　thermoelectricity　effect　and　summarize　the　common　preparation　methods　for　thermoelectric　functional　parts　in　TEGs.　Then,　we　elaborate　on　the　application　of　TEG-powered　sensors　in　the　human　body,　including　wearable　and　implantable　medical　electronic　devices.　This　is　followed　by　a　discussion　on　the　application　of　scene　sensors　for　IoTs,　for　example,　building　energy　management　and　airliners.　Finally,　we　provide　a　further　outlook　on　the　current　challenges　and　opportunities.