It's good to see how excited you are about that project. I have some questions:
You say several time in the video something like "I hope you see how this could be useful". But nearly every thing you show in the video could be accomplished in Visual Studio without restarting, recompiling or instrumenting the code. Could you state precisely in which case you think seashell is useful ?
It looks like it could be used as an in game console, if you provided an easy way to integrate it into any renderer.
For variables, is it possible to "watch" variables that exist only in a certain scope (inside a function, inside a loop...) when using the step functionality ?
I would be interested to know how does seashell pause the execution of the program ? But I can wait for the code release and find out myself.
A last note: by reading the description of the project I didn't get that seashell was a shell that "connected" to an application. The first video you posted made it clear what it was. So maybe update the description to clarify that.