The DT880 is a very popular phone power testing tool that lets you power iPhones/others directly via the battery connector using a multitude of adapters plugged in to the "USB-A" port on the DT880 ( not really working as a USB port though ).

The DT880 seems like it's no longer being produced so I created a replacement based off my existing USB-C current/voltage meter and added in the new aspects to suit the iPhones.

4.2V linear regulated output up to 3A
Clear to read 8x2 CoG LCD display
PC serial communications (9600bps)
USB-C power input ( no more dodgy USB-micro connector )
Power on/off button
Boot button