For the granita, in a saucepan over high heat, bring water to a boil. Remove from heat. Add coffee and sugar. Stir for a couple minutes until everything is melted. Set aside to cool for 45 minutes. Transfer the mixture to a flat-bottomed 7x9-inch glass deep dish. Keep in the freezer and chill for 45 minutes.
Stir the mixture thoroughly with a fork and freeze again for 30 minutes. Continue to freeze for another 3½ hours, scraping and breaking the mixture with a fork every 30 minutes. Cover with a lid or plastic wrap.
For the jelly, in a small bowl, add ½ cup cold water. Sprinkle the gelatin over and whisk for 10 seconds. Set aside for 5 minutes to soften.
Meanwhile, in a saucepan over high heat, bring water to a boil. Turn the heat to low. Add coffee, sugar and soften gelatin. Stir for a couple minutes until everything is melted. Remove from heat. Pour into a 9x9 baking dish (or 8x8). Keep in the fridge until jelly is set, about 4 hours.
When the jelly is set, dip the pan in warm water for 15 seconds. Make sure water doesn't get into the jelly. Then run a knife over the jelly to cut into ½-inch cubes. Flip the pan over a baking sheet and pound lightly for a few times. The jelly cubes should fall over. Keep them in an airtight container in the fridge if not use immediately.
To assemble, place serving bowls in the freezer for at least 15 minutes. Scoop granita into the bowls. Top with vanilla ice cream and add jelly cubes on the side. Serve immediately.