It doesn't really tie directly into it, besides insofar as the company I work for builds a web application and this thing would be directly useable by a web application. Think of something like analytics services - they're useful to a wide variety of companies but not to any one specifically unless they're involved in analytics.

Put it this way - my company would be a great client for this tool, but would never want to sell it themselves.

Very dangerous if your side project is related to your job (which it appears to be) your in danger of losing any IP.

Check your contract and applicable state law you may already have lost your IP - lets hope your employer will act in good faith.

I would make sure as part of negotiations that your employer pays for an independent lawyer to write up a new contract and to make sure that you license your IP to your employer and maintain your rights.