in my opinion, then best thing for tightening the stomach would be pilates, or pilates type exercises.

here is a website with a list of them. They are way more comprehensive and effective than a machine would be.

http://ourworld.compuserve.com/home...apowell/abs.htm

As for loose skin, if it's "flab" as in fat, you'd have to lose the fat for it to not be tight.
If it is SKIN that is loose, most people have to live with it, though I have seen awesome results using skin brushing on my chest.. as so noticable my husband keeps commenting on it and saying that my breasts grew. They didn't grow, they got higher. I'm still working on the stomach results, but have only been doing it for about a week and a half.
The other thing about stomach flab, you have to take your body shape into account. If you have a short torso (only a couple inches between your ribs and hip) you are always going to have a thicker waist than someone that has a lot of room between the ribs and the hip - because there is less room in your midsection for your organs and fat to be spread out. There doesn't have to be flab, but if you're short torso'd then it's going to be really hard to get rid of it all and have the hourglass.

Meg