What Toktumi has done is build a back end similar to that of Google Voice — but unlike Google, it’s gotten Apple’s blessing. It’s one of the more complete mobile VoIP apps currently available for download; I especially like the fact that it allows you to receive calls straight to your mobile phone over a cellular network even if you don’t have 3G or Wi-Fi coverage. It comes with its own features such as call waiting, conference calling, call transfer and even voice mails — in other words, the service is like a virtual second line on your phone. The service costs $14,95 a month for unlimited calls in the U.S. and Canada.

Toktumi, which launched at DEMO 2008, has had to traverse a difficult path to get to where it is today, and Sisson is understandably excited about the kind of exposure the approval from Apple of its app will bring. Sisson, a veteran of the VoIP business, sold his last company, Teleo, to Microsoft.

Skype for iPhone could debut at the CTIA Wireless trade show that begins April 1 in Las Vegas next week, Malik speculates. Industry watchers have anticipated an iPhone version for some time, particularly since the popular service already runs on other mobile devices. In addition to Skype for Windows Mobile and Skype Lite for Java phones, there’s a version for Google Android phones like the T-Mobile G1.

While Skype’s mobile ambitions are good for iPhone users, the VoIP service won’t bring the end of standard voice-call service anytime soon. As PC World’s Liane Cassavoy reports in a recent review of four mobile VoIP apps — EQO, Skuku, Skype for Windows Mobile, and Truphone — mobile VoIP call quality isn’t quite there yet, and the cost savings aren’t that great.

“Most notably, the call quality remains iffy at best, and in some instances it’s absolutely abominable. Also, depending on your calling habits, you may not see any savings at all. Most services still charge a per-minute rate, so you’ll save on domestic calls only if you’ve exceeded your regular voice plan’s allotment (in which case you might still be better off upgrading your voice plan).”

Cassavoy does point out, however, that international callers can save big bucks by using a mobile VoIP service.

While Skype for iPhone may not offer immediate benefits for everyone, the service has plenty of potential in the near future. If the next-gen iPhone, which may appear as early sometime this summer, includes video capture, Skype could turn the iPhone into a portable video conferencing device. That may not happen immediately, of course, but AT&T’s upcoming 4G Long-Term Evolution (LTE) broadband network, slated to debut in 2011, could very well have bandwidth necessary to make two-way, real-time video a popular app, particularly among business users.