They have, ts. Everyone I know around here has a couple of pairs. Mine have coils of metal instead of spikes and they work a charm. Really came in handy this year as we have had to deal with ice for over a month now.
They have not shown if people are able to walk on snow with this. But if this is good enough to provide enough friction on snow, I think this is a good invention. Doesn't appear so costly and can really save you from a bit of embarrassment that you might undergo while slipping on snow. Also, it can help people prevent injuries as well. But the most important question is, is it that effective?