Arrange the oven racks in the center and lower third of the oven. Preheat the oven to 350 degrees F. Nestle the peaches, cut-side up, in a small baking dish. Drizzle with the honey and dot with 2 tablespoons of the butter cut into small pieces. Pour 2 tablespoons water into the bottom of the dish and cover tightly with aluminum foil. Place on the center rack and bake until the peaches are soft, 25 to 30 minutes. Let stand, uncovered, for 5 minutes.
While the peaches bake, make the crumble topping. Put the graham crackers in a small plastic bag and coarsely crush with a rolling pin or can. Melt the remaining 2 tablespoons butter in a medium bowl in the microwave. Add the crushed graham crackers, pecans and sugar and toss until the sugar is dissolved and the mixture is combined. Line a baking sheet with foil and spread the crumble mixture on the sheet. Bake on the lower rack until toasted, stirring every 5 minutes, 12 to 15 minutes. Let the crumble cool on the sheet; it will continue to crisp as it cools.
For each serving, put 2 peach halves and a spoonful of juices from the pan in a shallow bowl and top with a spoonful of ice cream or yogurt and a sprinkling of crumble.