If so, you can always get him a nerdy watch. Nerd watches are big business. There are even online discussion boards dedicated just to Nerd watches. For example, you can visit the Pocket Calculator Show's Nerd Watch Message Board to learn all about vintage nerd watches. They have the coolest collections of interesting and obscure digital watches.
As for me, I only have one genuine nerd watch. It's a Casio Calculator watch. These watches are dirt cheap at Walmart and make a great bonus gift or stocking stuffer at Christmas. If you haven't read it yet, here's my review:
Wristwatch Review: Casio Calculator and Calendar Watch
If that's not nerdy enough, you could always find a vintage slide rule and a book like this one: