I want to describe a few of the things I've done for and with my kids this school year, so that you can borrow my ideas if you like them.
First, I took a notecard. On the outside I wrote "Information Inside" and then their bus number and their PIN, which is used at school for a variety of things. On the inside I wrote, the kids names, address, phone number, and school. Then I wrote our names, our phone numbers, my Dad's name and phone number, and any pertinent medical information (MG is allergic to amoxicillin, for example). I stuck this notecard and some money (a $5 bill and a couple of dollars worth of loose change) inside a Ziplock bag in their backpacks.
So, if they get lost and they're freaking out and blanking on our phone number, it's there. If they forget their PIN for lunch, it's there. If, knock on wood, they're unconscious and someone is looking for identification in their backpack (after all, 5 and 7 year olds don't have state issued photo ID, right?) it's there. I really doubt that anything will happen, but it's just a notecard... No harm, no foul if it's there and they never need it.
As for the money, I don't think anyone should ever leave the house without some way of paying for things. If they forget lunch and their account is empty, they have emergency lunch money. If there's a bake sale or something unexpected at school, they have money. I think they're old enough to handle a little pocket money, and I'm not worried about them buying $5 worth of ice cream from the ice cream truck because they think that it's a music truck that drives around in the summertime to make people smile. I really need to quit lying to my kids...
Anyway, the other semi-brilliant thing I did is a little more of a commitment. Since I'm going to be home about 175/180 school days to retrieve my kids, I let the neighborhood kids know that if they need a safe place to go and their parents aren't home, they can come to me. The bus stop is on my corner and I'm there, anyway. I gave the parents names of a couple references in our neighborhood - friends of mine who know that I'm trustworthy - and said, "If you get home and the door is supposed to be locked, but it's open, come to my house and we'll deal with it together. If there's a car you don't recognize... If there's a storm... If you need help with your homework... Any time you just don't feel right going home for WHATEVER reason, you can come to me and we'll figure it out together." The parents of little kids know that if they are delayed getting home and aren't going to make it to meet the bus, they can call me and I'll grab their kids and feed them a snack and keep them at my house until their parents get home.
It's so much easier for everyone to arrange these things in advance.
Now I'm not saying you need to be the block parent for your whole neighborhood, but if you've got some neighbors who have kids and you're going to be around most days, why not let them know that you're a safe place to go in an emergency? If you have kids who are out in the world, why not find a neighbor who is willing to be their safe place, too?
I know I'd rather have the whole neighborhood at my house every day than have some little kid alone and scared at home. And there's a storm today, so we might just see who shows up!