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.
Note: 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.