If you are a locksmith or a pizza shop mobile search ads which drive conversion oriented calls are highly valuable. However for businesses with more complex sales funnels desktop visitors have a substantially higher visitor value than mobile phone users. In August of 2016 TripAdvisor executives stated their visitor values on desktop and tablet devices were similar, but cell phone visitors were only worth 30% to 1/3 as much. Smaller businesses likely see a deeper click value discount on smart phones and other small mobile devices where typing (and thus converting) is hard to do.
Long Tail Pro is a very useful piece of software for long tail keyword research. One of its best features is that you can carry out heavy analysis on the keywords of your choice, without being limited to only working with one or two at a time. It can provide you also with vast numbers of longtail keywords, or you can apply filters to find the precise keywords to fit your bill. And you can check your rankings at the same time!
Long Tail Pro is a keyword research tool that helps you quickly find low competition keywords for your website. In particular, the tool is built for people doing SEO (search engine optimization) as opposed to people doing paid ads (Google Adwords PPC). I'm sure there are some advertisers that use the tool for paid ad keyword research, but the tool was built for SEO keyword research.