Not aware of any hobbyist or prosumer stations that provide a direct readout of moisture content in the air, though of course it is easily calculated from humidity and temperature readings.
Davis Weatherlink for Windows software always used to provide a parameter called EMC - equilibrium moisture content. I've never had cause to use or look into this myself but it might (?) be what you're after. This is a computer calculation though and not a station console readout. I don't recall seeing this parameter on the Davis weatherlink.com platform but I guess it might be there.