Yep, great idea, because I do it as well. Has saved me once or twice. One of the most memorable times I locked my keys in the car, was when I was at the post office, and I parked and filled out the address to one of the letters I was mailing. I got out of the car to put it in the mailbox, and when I got back I realized that I had locked my keys in my still running car. I went and leaned up against a railing next to my car and lit a cigarette to stop myself from freakin' out. I guess I looked really worried, because the next thing I knew a guy comes up to me and asks me if anything was wrong. I looked at him and told him my keys were locked in my car. He then says, "Lucky you," and explains that he happens to be a locksmith, and I look over and see his work van parked right next to my car. He got me out in about a minute, and I offered him some money, but he said it was too much of a coincidence for him to take it. Lucky me.