1) Great idea (thank you), but he already has GPS
2) Under $100 - he wouldn't want me to spend more
The problem is, if he really wanted something he would just buy it. So its all about finding something that he would like, but never buy for himself because its just not necessary. You know?
Maybe concert tickets. My dad buys 2 tickets to any concert he wants to go with and always invites my brother or i at the last second. I've been to some SICK concerts with him. In the last year... The Who, Van Halen, Audioslave, etc... maybe I'll do that.