DaVinci makes SF, caffeine-free chai tea syrup that is ideal for lattes. I found it at TJ Maxx, but you could order it through
www.netrition.com, too.
For a frappuccino (those are icy, right?), you could make your own with the syrup, milk and ice in a blender!
I have a funny story about those Cinnamon Dolce lattes at Starbucks. I ordered one, sugar-free, nonfat, and watched as the barista made it correctly, then proceeded to top it with a monster cap of whipped cream. I mean, duh, if someone orders an otherwise vice-free drink, would they really want whipped cream?
Made correctly, those are yummy drinks, though I usually use my own butter toffee SF syrup for lattes.