Since public charging infrastructure is a shared resource, I would just be cautious and judicious about usage of such locking tools. Getting back to your question, no, don't have one and a situation where something like this might have been useful for me would have been ... once, in my 2.5 years of BEV driving? Of course, your situation may vary; dsmith probably has an argument to be made that something like this would be useful in his case.