Got me thinking how tied up with technology people are-- almost hampered by it now. Can't move without something attached or hanging off the body...Ipod, Blackberry, might as well be set up for cyber-conversion
So let me ask you this...
The Doctor travelled (meaning mainly Tom's Doc) with simple (if not many) items in his pockets. The only 'technical' item was his sonic screwdriver. The yo-yo, the deck of cards, the magic wand etc. were all everyday items meaning 'no batteries required'.
With that in mind, which electronic-techno gizmo would you have to have with you if you could only have one.