I do...it's just one of the standard pen-type with the plunger that extends to show the pressure. I gave my wife one of the digital ones for her car since I figured it would be easier for her to use.
I carry a stick kind from Campbell Hausfield, my wife has a dial type that stays on the registered pressure until you reset it, kinda nicer I think. Don't know the brand though.
Yup, there's always on in it. And one at the house with the other air tools. Dial type at home, stick type in the Titan. Don't know what brands either of them are though!