A basic version of this already exists from Monoprice: http://www.monoprice.com/product?p_id=13166 http://www.monoprice.com/product?p_id=13166 Plug in a microU

A basic version of this already exists from Monoprice: http://www.monoprice.com/product?p_id=13166 http://www.monoprice.com/product?p_id=13166 Plug in a microUSB device and it can only charge; you have to hit the button in order to enable the data pins. But I think this is designed for risks going the other way, i.e. to protect your cell phone from data-scraping USB-A female ports in airports and the like.