The issue I usually have going on a jog is that I can't bring keys or any item without having to have to carry extra weight, which is why Bag on Bottle is a great accessory to have.
Maria Härdig's Bag on Bottle is a miniature pouch that straps itself to a water bottle. Think of it as a coffee cup sleeve that doubles as a wallet. While it can't hold a wallet, it will hold cash in one place so that joggers don't have to dig around their pockets when they need to buy things on the run. If not money, the compartment is big enough for a cell phone and keys.
The Bag on Bottle is a great item for joggers who want to carry certain essentials without the weight bearing down on them.