After Google AdWords launched their enhanced campaigns, targeting only mobile devices has become tricky. The way Google has built the new Adwords interface and campaign settings hints that they want you to create universal campaigns which will run in all the devices, without much options for device targeting.
However I want to run the ad only on mobile devices. How do I achieve it? Right now there is no option to setup a campaign only for mobile and there is no option in the campaign settings to turn of computers and tablets completely.
There is an approximate work-around to target only mobile devices in Adwords PPC ads, and this is the method that I use. In the campaign settings you can change the bids for mobile devices, computers and tablets.
If you are running a campaign only for computers and tablets, you can decrease bids for mobile by 100% which would turn of ads in mobile.