Non-invasive skin tightening
There are several non-surgical skin tightening treatments being used today: thermage, ulthera, and thermiRF to name a few. All of these treatments will tighten the skin of your abdomen, but I don't think it will be to an extent that you will be satisfied. Depending on your goals (if you want the abdomen tight and flat, or if you just want to remove the role of skin between the belly button and pubic region) you might be a candidate for a mini tummy tuck.
Thanks for your question and best of luck!