https://www.theverge.com/circuitbreaker/2018/10/16/17967012/huawei-mate-20-pro-reverse-wireless-charging-smartphone

Once upon a time, wireless charging was a rarity in phones. As of today, though, not only do we have fast wireless charging in the iPhone and many Android flagships, there’s even reverse wireless charging, courtesy of the freshly announced Huawei Mate 20 Pro. I tried this out in London ahead of the new super flagship phone’s launch today, and it works beautifully. You just enable the option on the Mate 20 Pro, and any time the device is pressed against another that supports Qi wireless charging, it automatically starts transferring power. That’s all there is to it. It’s obviously not going to be fast, and it’s probably not going to be super practical, but the Mate 20 Pro does have a sizable 4,200mAh battery, and the ability to share that out in an emergency still counts as a pretty cool feature.