Can Vaisala humidity instruments output parameters other than relative humidity and temperature?

Yes.  The HMT330 transmitters and the HM70 hand-held meters measure relative humidity and temperature. From these values dewpoint, mixing ratio, absolute humidity, wet bulb temperature, enthalpy, water vapor pressure and ppm can be calculated.

The HMT100 also measures humidity and temperature, and can be ordered with a  dewpoint output.