There's nothing to stop you using a hybrid equilibrium constant including aqueous concentrations and gas pressures, especially since the usual standard state for solutions is 1M concentration and for gases 1 atm pressure.

For example, the Nernst equation (which is related to equilibrium constants) for the H^{+}/H_{2} electrode would be

E = E° + RT/F*ln([H^{+}]/p_{H2}^{1/2})