Nice work Alain,

Another idea : do not show the thief the "STOLEN UNIT", but let him think the PIN was correct. Then let irDA try to call a specific number over an irDA-enabled mobile-phone every 5 minutes.
I guess someone has to walk by sometimes with an irDA enabled telephone and IR reception on. Through caller number identification you could locate the unit.

As for the upgrade program I do not think this is possible as it is in ROM.

Frank van Gestel