My mobile computing environment is primarily an iPad Mini and an iPhone 5. Coupled with an Apple Lightning cable and a 12 volt power adapter, my entire computing environment moved from a laptop bag into the pockets of my Seattle rain jacket.
A creature of habit, I simply leave the cable and adapter in an out of the way pocket in the jacket so I never forget them. The iPad Mini easily fits into one of the larger inside pockets in the jacket, protected from the weather, easily out of the way when walking, and comfortable enough I can sit down without pulling it out unless I really need it. Going through a TSA check point is more convenient than ever since I simply remove my jacket and send it thru - no need to remove the iPad Mini or iPhone from the jacket pockets.
I always had a thin & light laptop (Macbook Air) but the bulky power adapter, requisite USB cables, headphones, and mouse made it easy to justify carrying around a lot of other crap like a note book, additional pens, business cards, disk-on-keys, and storage for anything else I needed.
The iPhone and iPad Mini add less than 2 pounds and I was able to give up a 15 pound laptop and bag.