Now developer Toktumi has released Line2 HD, an iPad-specific version of the app, which should prove popular among business users. It not only turns your tablet into a full-featured phone, but also provides a nice hub for managing calls and messages.
To get started with Line2, you need to sign up via the company's site. (Unfortunately, there's no longer an in-app sign-up option.) You can test-drive the app and service with a free seven-day trial.
Once you've exhausted that, Line2 offers two main service plans: Standard and Professional, priced at $9.95 and $14.95 per month, respectively. (Discounts apply if you prepay for a year.) Both plans entitle you to a new or transferred phone number, unlimited local and long-distance calling and texting, and visual voice mail (including message delivery via e-mail, a great feature).
The Pro plan adds a virtual receptionist, an auto attendant, and the option for a toll-free number, among other things. The $150/year rate for that plan is in line with what you'd pay elsewhere for a business-oriented phone service.
The app itself is pretty straightforward: tap New Call to place a call or New Message to send a text. The more you use it, the more you'll appreciate the detailed history Line2 gives you for calls, voice mail, and messages--the kind of information prized by many business people.
Speaking of business, the app supports conference calls with up to 20 participants. You can also toggle a do-not-disturb option if you want to route incoming calls directly to voice mail, like when you're stepping into a meeting. And if there's no Wi-Fi or 3G connection available to your iPad, Line2 will automatically forward calls to up to six other phones.
In my tests over a Wi-Fi network (my iPad lacks 3G), calls went through and were received very quickly. Even better, sound quality was excellent at both ends, even when using the iPad as my speakerphone. You can also plug in a corded headset, of course, but if you want to go the Bluetooth route, you'll need an iPad 2. (That's an Apple limitation; the iPad 1 doesn't support the Hands-Free Profile.)
There are, of course, countless other apps that can endow an iPad with voice capabilities, most notably Google Voice and Skype (though the former has been pulled from the App Store owing to iOS 5 incompatibility). But I like Line2's presentation, call quality, and business savvy. It's a compelling option for anyone looking to turn an iPad into an iPhone.