Combine all ingredients in a shaker and shake over ice. Empty the shaker and ice into a fresh glass. Garnish with a slice of fresh peach or grapefruit peel -- if you want to get really fancy, flame a citrus peel and watch your friends and family 'ooo' and 'ah' at your skills.
For the peach simple syrup:
Combine water and sugar in a saucepan over medium-low heat. Once sugar is dissolved, add peaches and let simmer about 5 minutes until peaches are infused. Strain into an air tight container.