For my one piece surf rods I've got a piece of 4" PVC with a cap glued on one end and a ground water monitoring well locking pin on the other; I run a small cable through the lock and then my Yakima bars. It's easy enough to cut a piece of PVC with a string but it'll keep most folks from messing with them. I take the reels off. My fly rods are two piece and travel in a rod case, my spinning rods travel behind the seat or tossed on top of my sleeping bag in the back.
Two piece rods will travel fine set up. I use rubber bands to hold the pieces together and slide them into a rod sock or a gun case. A soft pistol case works great for a travel or light telescoping rod setup with a reel and lure, even in a saddlebag or backpack. There are some surprisingly decent telescopic rods available. I keep one in each of my hunting and work trucks for quick access when I don't want to take time set up one of my "better" rods.
I'll admit it has limitations though. It doesn't work the best in vehicles with sun/moon roofs because of the different ceiling heights. I think it would work pretty slick in a long vehicle like a Suburban or in a situation where no one ever sits in your third row. It's also kind of pricy, unless you find a deal somewhere. I got mine for about half price, so I'm pleased.