I agree with chris - hard to give someone a hobby. But I have given gifts of "letterboxing kits" in the past that people have enjoyed. Letterboxing is the old-fashioned version of geocaching.
If he likes hiking in interesting places outdoors, solving clues, writing clues, crafty stuff (you get to make your own stamp), he might like letterboxing.
I usually include carving tools, some rubber material for carving stamps, a nice notebook for "stamp collecting," a box to keep it all in, and the Letterboxer's companion book. The link below provides much more info.
http://www.letterboxing.org/GettingStarted/
