Remove as much of the corn silk as possible. Trim off the stalk ends from the cob. Stand the ears up on a cutting board and, using a short sharp knife, shave off the kernels. Get as much of the kernels as possible without cutting into the cob and be careful, the kernels have a tendency to fly all over the kitchen.
Put the corn kernels, mussels, and 1/2 cup water in a wide deep skillet or Dutch oven. Cover and bring to a boil over medium-high heat. Steam, shaking the pan occasionally, just until the mussels open up, 3 to 5 minutes.
While the mussels are steaming, toss the tomato, red onion, yellow pepper, cilantro, olive oil, garlic, chile, and lime juice together in a bowl. Season with salt and pepper, to taste.
When the mussels are open, scoop them out with a skimmer and put them in a serving bowl large enough to hold them comfortably. Add the tomato mixture to the mussel steaming liquid, give it a quick stir and pour everything in the pan over the mussels. Serve hot, warm or at room temperature.
Most mussels found in markets today are 'cultivated' meaning that they are raised in a controlled environment and are much less likely to be muddy or to sport "beards," the wiry growths that protrude from the shell. If the mussels you buy have beards-you'll find them sticking out from between the shells about halfway down the flat side of the mussel-simply give the beards a good, firm tug to remove them. In any case, it's a good idea to rinse the mussels in a colander under cold water before cooking them.