We get a lot of requests to include specific Photoshop tools in Sketch. I have to admit that the Magic Wand, at least in my time on this team, has never been requested so, therefore, I've never heard it being discussed as a feature in the app.
Although I'm pretty sure it's not in the team's plans to incorporate Photoshop tools "as is," I know that they do consider these types of requests with regard to a particular tool's usefulness with regard to drawing in the app... so I'm more than happy to share your idea/comments with them.
Sorry I don't have a more insightful response.
Thanks for your response, Sue. I hope they will consider it, and I should add that it wouldn't be that useful unless there was also the "select inverse" option added somehow. If we are continuously adding transparent color over what's already been drawn, this would save a lot of time.
I'll definitely share this with the team. It makes a lot of sense.