Yeah, I think the presence of technology is essential. Without it, you have a classic fantasy set in a city. The Hawk and Fisher books by Simon Green, and Cook's series about the private investigator that I can't currently think of the name of. They are gritty storis set in an urban setting, but they are not really urban fantasy.
It does not have to be modern day tech, however. Lillity Saintcrow's Dante Valentine series is an Urban fantasy set in the future.
Just my 2 bits worth.