How to Make It
Combine first 3 ingredients and 1/8 teaspoon salt in a small saucepan; bring to a boil. Remove pan from heat; cover and let stand for 30 minutes.
Place 1/4 cup 2% milk in a medium bowl. Sprinkle gelatin over milk; let stand 10 minutes.
Return pan to medium-high heat; bring to a simmer. Add hot milk mixture to gelatin mixture, stirring until gelatin dissolves. Add remaining 3/4 cup 2% milk. Strain mixture through a fine sieve into a medium bowl; discard solids. Stir in 1 tablespoon Key lime juice. Divide mixture evenly among 4 (4-ounce) ramekins or custard cups lightly coated with cooking spray. Cover with plastic wrap, and refrigerate overnight.
Combine remaining 1 tablespoon juice and honey.
Melt butter in a small skillet over medium heat. Add crumbs and remaining 1/8 teaspoon salt. Cook 1 minute or until lightly toasted, stirring constantly. Cool completely. To serve, loosen edges of panna cotta with a knife or rubber spatula. Invert ramekins onto dessert plates. Drizzle each with about 2 teaspoons honey mixture, and top with about 2 teaspoons graham cracker crumbs.