[phil21]

In general most (all?) USB-C phones support USB power delivery. This means when you plug in two phones to each other, they will prompt you on-screen asking if you want to charge the connected device.

I'm not sure what you mean about charging a USB-C Bluetooth keyboard? If you mean can your phone charge a random USB-C peripheral the answer is generally yes.

You can even use your phone to charge your laptop if you like, although I don't know why you'd do that :)

One awesome thing with USB-C I've found is I can simply use my phone charger for trickle charging. I rarely take my power brick out of my laptop bag these days, since that's more than plenty for most uses.