Off topic, but I recently found the pressure altitude on the Garmin transponder to me most handy too when I lost my altimiter and every other instrument.
Also a reason why encoding altimeters in an IFR or NVFR aircraft are a bad idea. At least with a blind encoder ATC will see something other than you if either fails. Between the both of you, you can then work out which one to trust.
(From a recent edition of EAA Sport Aviation, where they described an actual crash that probably would not have happened with a blind encoder.)