In deep-fryer or deep, heavy pot, heat oil to 350° F. Wipe hot dogs dry with a paper towel so that batter adheres better. Insert a chopstick into the end of each hot dog. Mix tempura batter carefully with water according to package directions. Dip each hot dog into batter, swirling to cover the whole hot dog and a little of the chopstick. One at a time, drop into hot oil and fry 3-4 minutes or until crispy but not brown. Serve with curry mustard.