maybe try the lowest possible impact things, like standing and walking in place while making little circles with your hands, with your arms stretched out at your side. If sitting, hold a can of vegetables or soup in each hand and slowly curl them up to your body, then up toward the sky and back down and out. sitting in a chair, lift your legs and hold them, one at a time and both at a time. Do anything you can to bend forward and backward, then just get up and walk around the room, or the house. This is what you'll want to do post-operatively if you have carbon dioxide gas pumped into your abdominal cavity before surgery. The only way to get it out is through the skin, and the only way that happens is through movement. otherwise you'll have a lot of weird painful stabbing in places you don't expect it.
by far, walking is the best, but don't do anything that would hurt your knees, hips or feet. You'll take on more as you heal and lose weight, but you're not ready for situps or aerobics. In several weeks, maybe start swimming. It's no impact and burns calories like crazy. I think it's actually the most calorie-intense activity of all you can do. and it's great if you're overweight because you're buoyed up by the water, so you feel weightless.