From Goodyear's FAQ:
All Goodyear blimps are FAA-certified for IFR (Instrument Flight Rules) flying, day or night. They carry two King 360-channel navcom radios, the usual light plane instruments, digital radar for keeping an eye on thunderstorms, transponder for radar identification, and a couple of instruments peculiar to blimps: manometers for watching envelope pressure and a helium temperature gauge. All Goodyear Airships carry GPS navigation receivers for precise navigation.
John King has some interesting stories about flying an ILS in a blimp - the best part was his crack about worrying about the weather behind you.