I like this idea a lot. I've been thinking a lot lately how great it would be to have something like Flowsheets where you have a spreadsheet and language working together. This REPlugger closely matches a lot of how I end up writing code, with putting things over and over again into the REPL and seeing how they worked. I always wanted a REPL that could edit better. This is very cool and I think could be amazingly useful.

Edit: Found the github link in the video description: https://github.com/Glench/REPLugger