Heat the grill to medium-high (which means you can safely hold your hand about 4inches from the grill rack for about 4 seconds). Place the pineapple slices in a single layer on the heated grill rack. Cover and cook for about 3 minutes, until there are golden brown grill marks on the underside and the bottoms look caramelized. Using a metal spatula (two make it easier), turn the pineapple, cover, and grill for about 3 minutes until golden.
Transfer the grilled pineapple to a cutting board. Cut each slice into small dice, and place them and their juices in a small bowl. Add the remaining ingredients. Gently stir to combine. Serve warm or chilled.
Refrigerate any leftovers for up to 2 days, stirring again to combine just before serving.