Most GPS navigators are TSO C 129 except for the CNS 480.

129 units are considered secondary navigation devices.

The consequence is that you must have VHF navigation for
an alternate and pick an alternate that is not GPS-only for
approaches. BTW, that is why you still have to do your vor
checks even tho you nav by GPS everywhere.

Donno about that missed approach business... haven't heard that
one.

Bill Hale