How can I film my two hands? In filming a video diary, I am often trying fruitlessly to put my two hands in the frame (as I stand, walk, etc) to show in the video when I am doing certain things with my hands. 

It is difficult to achieve, as I have tried with iPhone and with DSLR/mirrorless cameras as well as with camcorders, and holding the device, as well as seeing the screen to frame and focussing were all very difficult.

Has anyone achieved this? I would love an answer that explains solutions on how to do this with an iPhone as well as with a DSLR/mirrorless camera. A tripod cannot be an answer, unless if it fits on my head or shoulders.
Go Pro offers both headbands and helmet mounts for their cameras.  Once you learn how to position and aim your head-mounted camera based on what you want it to see, you then only need a mechanism to start/stop the camera.  WiFi support and an appropriate app can be helpful.