Dude, FTA......there's no app that will substitute the education you should be seeking......... With all do respect, stop trying to make tree care something you take your smartphone out for. There are way too many respectable, educated arborists that have spent time and money learning arboriculture correctly, and provide a service based that solid background.
Grab the copy of Dirr, Woody Plants. Then get yourself a Peterson's field guide (for the West Coast, I would imagine
) It might also behoove you to grab a few other books listed on the ISA's website. They will help you greatly.
Sometimes arborists get stumped on something they haven't seen in a while, or something exotic, or even something stupid, as an ID. But walking back to the truck with a twig in hand that you have CUT off with a nice little pair of felco's to look at a book is WAY more professional than taking out the smartphone and saying to the client, " Well, my IPHONE Says....."
-My Dollars Worth.....
-Mike