We do this be using the MPLAB / ProMate SQTP files.

They are intended to burn in a serial number, but the SQTP format is
just a hex record that overlays a bit of the code space and
automatically goes to the next record for each PIC.  We put a serial
number in, but you could easily put in a version string and serial
number by editing the automatically generated SQTP file or just
creating your own.  We insert RETLW tables, of course, then its all
available using the "usual" constant string method using
CALL + computed GOTO + RETLW table.

------------
Barry King
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
barry@nrgsystems.com
Phone: 802-482-2255
FAX:   802-482-2272