I carry a 10000 mAh battery pack[1] in my jacket[2], which besides powering the heater elements inside the jacket also provides wireless charging to my phone.
I don't know about effectiveness, but 20-30 minutes of wireless charging gives 60% + of battery power on my phone, and while i don't regularly charge my phone fully in the jacket, only top it off, i charge the battery pack once every week or so, and it is very rarely at 0%