> If you're using melodies and samples from work hours, then maybe not.

That would not be a question of competition, but of IP theft.

> And it would be tough to argue that your at-home trading app code is completely uninfluenced by ideas you have at work.

How is that of any relevance? I can have ideas about a better way to wipe my ass at work, is my novel ass-wiping implement competing with the company?

And even if it were, mere competition should not be enough for NCCs to trigger. NCCs should be about unfair advantage owing to the exploitation of sensitive or confidential information.