Call only is not the only way you can have a mobile campaign, as per the above video, if you add a bid adjustment for mobiles of 300% and have mobile text ads and extensions, it is going to be heavily dominated by mobile devices.
Also if you have a corresponding desktop campaign (a duplicate) which has mobile off, you have essentially segmented your campaigns by device.
In practice, occasionally you do get a few impressions on the mobile campaign on desktops and tablets, but generally speaking, this works pretty well at keeping the devices separate. Only thing to remember is bids are 3 times higher than what you input, so if you want to bid 30p, then enter 10p on the keywords and the bid adjustment for mobiles will increase it to 30p.
The more granular or segmented you make your campaigns, the easier it is to see how everything is performing, I would not necessarily recommend this approach to everyone, but I think it could benefit quite a few accounts where mobile is either outperforming desktops, or is quietly wasting your budget without you realising. Either way, to give you the best chance of success optimising a campaign for mobiles is certainly worth a test.
About the author
Thomas Green is a Certified Adwords Professional and specialises in direct response marketing. He has over 6 years PPC experience and has a straight forward approach to what works and what doesn’t!