As others have pointed out, it's not the recording that's the hard part per se; more so the entire workflow from hitting firing up the recording tool to getting the final recording -- possibly edited -- into the cloud for sharing in some seamless flow.

Lots of ancillary stuff involved. I know a team that went down this route and built a competing tool and the hardest part was working out the streaming upload and storage. Then you layer on things like permissions, lifecycle management, etc.