A long time ago, on one of these two mailing lists, someone asked about
Ada for the Palm Pilot.  The best responses only said (if my middle-aged
memory isn't failing)  that if you can find a gcc port, adding GNAT
shouldn't be too hard.

Well, I just stumbled onto http://www.geocities.com/SiliconValley/Horizon/5249/GNU_Pilot_SDK.txt

Here's an excerpt (paragraph 2.1):

GNU gcc is a very popular and free C/C++ compiler available for just about
any platform with more than 2 bits on the chip.  prc-tools was born when
gcc was ported by D. Jeff Dionne and Kresten Krab Thorup to cross-compile
for the Motorola 68328 Dragonball processor.  Various utilities in prc-
tools were done by Dionne and Ian Goldberg.  Dionne is the current
maintainer of prc-tools.  The current version of prc-tools is 0.5.0.,
corresponding to gcc version  The official prc-tools archive with
Linux versions is at <URL:ftp://ryeham.ee.ryerson.ca/pub/PalmOS/>; you'll
need the following GNU utilities at <URL:ftp://prep.ai.mit.edu/pub/gnu/>:
gcc-, binutils-2.7, and gdb-4.16.  John J. Lehett has ported these
tools to Win32; you can find this version through <URL:http://www.land-