INAL but I wouldn't mention anything to your employer. They will either want the IP and/or use it for free and most likely let you go if it replaces your job.

INAL but I wouldn't mention anything to your employer. They will either want the IP and/or use it for free and most likely let you go if it replaces your job. If you think your product has legs I would co-found with a marketing person, you can handle the tech side behind the scenes, keeping your name off the public facing side. Make sure you're not developing, testing or using your product at work. I would let your cofounder market it and be the face of the product. Oh and don't even offer it to your current employer. Good luck.