I simply couldn't choose just one, so I sketched both my iPad and my sketch kit. I use them both every day to make and publish my artwork. Actually there are three things that I carry with me and use daily. My phone is the third in this trio of essentials.
Note: I have been so busy this past week and upcoming schedule is just as jammed; so even if I sketch each day, I may not be able to post until my calendar clears up a bit. At this very moment, I am prepping for a two day workshop I am teaching at Kirkland Arts Center this coming weekend.