Even if this benefits those dang stupid people and their dang phones most of all, I think I'd be happy with it if it means potentially preventing me from doing something we are ALL prone to doing: occasionally screwing up.
Jesus fuck, THANK YOU. I walk to work every day, and I cross a busy dual carriageway, and at least 10-15 roads. I pay attention, but there will be the odd time when a song comes on my phone or a text comes through and I'll be momentarily distracted enough that I miss a crossing that this would stop me doing.
If occasionally losing 100% focus on what you're doing is "stupid", there's not a clever person on this earth.