Bountyhunter,
The cart idea is great. I'm not sure I want to carry one with me everywhere :-), but maybe I might be able to work something into my car kit or something.
Matt,
Did you mean backpack or did you really mean harness? I can imagine your dog being miserable if he was running around with cans tied to his harness! :-)
BTW,
here is a thread on CPF which has some info about a pretty cool harness.
-john