I'm working on a t-shirt design that notifies interested parties that audio and video recording devices may be in use. I also want to put a similar sticker on my car, and have a camera ready. There are too many people out there who will lie about their interaction with us in ways that can land us in hot water. Having the unbiased third party that is a video camera involved would, it seems, mitigate the risk of such unethical (and possibly illegal) behavior.