well, some GPS units don't work in the air (I thought of buying one for doug too this year).. i'd get him a gift certificate from an FBO so he can use it for a new headset or for flight lessons... but i really have no idea if the FBO even gives gift certificates!! hahaha
take a look at sportys.com - they have some interesting yet useful gifts on there like jeppesen manuals (I think)... cockpit posters.. manuals.. and what not...
they have a student pilot store on there too...
http://sportys.com/takeoff/