A recent AdWords announcement says click-to-call is available to advertisers nationwide via phone extensions:
“Recently, we announced new click-to-call phone numbers for local ads that appear on mobile devices with full internet browsers, like iPhone, Android or Palm Pre. This week, we’re bringing the same click-to-call benefits to national advertisers through phone extensions. Phone extensions allow you to add a phone number that will be displayed whenever your ad is triggered, regardless of the user’s location. Your number will appear as the last line of any ad text within existing or new campaigns. This enables customers to connect with your business by phone directly from the ad and can be especially useful if you have a call center to handle customer inquiries.”
Per AdWords help section about phone extensions:
To enable phone extensions on your text ads, follow these steps:
1) Sign in to your AdWords account at https://adwords.google.com
2) Go to the Campaign Settings Tab for the campaign with the ads for which you want to show a click-to-call phone number on high-end mobile devices with full Internet browsers
3) In the Networks, Devices, and Extensions section, under Devices, look make sure that your selection includes ‘iPhones and other mobile devices with full Internet browsers’ (if it says ‘All’ these devices will be included).
4) Under Ad extensions, click ‘Edit’ beside ‘Display click-to-call phone number on iPhones and other mobile devices with full Internet browsers.’ Then click the Save button.
5) Enter a phone number by selecting the option under Extensions to add a click-to-call phone number to your ads on mobile devices, entering a phone number, and clicking the Save button.
NOTE: I would suggest acquiring a unique number for phone extension display, so you can track close ratio on your end as well.