In a measuring cup or bowl, sprinkle gelatin over 1/2 cup (125 mL) of the milk; let stand for 5 minutes to soften. In a small saucepan, heat remaining milk over medium heat, stirring often, just until steaming. Add gelatin mixture, reduce heat to low and heat, stirring, for about 1 minute, or until gelatin is dissolved. Pour into a large measuring cup or bowl; stir in salt, honey and vanilla and let cool to room temperature.
Meanwhile, drain peaches, reserving 1 tbsp (15 mL) of the juice. Measure 3/4 cup (175 mL) of the peach slices; cover and refrigerate remaining peaches for garnish. In a tall cup using an immersion blender or in an upright blender, purée 3/4 cup (175 mL) peaches and reserved juice until smooth (you should have about 2/3 cup / 150 mL purée). Stir into cooled milk mixture.
Pour into four 3/4-cup (175 mL) ramekins or other bowls. Cover ramekins and refrigerate for at least 3 hours, until set, or for up to 2 days.
Just before serving, cut reserved peaches into thinner slices. Set ramekins in a shallow dish half-filled with hot water for 1 to 2 minutes. Wipe dishes dry, run a knife around the edge of panna cotta and invert onto serving plates to unmold. Garnish with sliced peaches and sprinkle with cinnamon.