Wouldn't it be cool if Words with Friends had a built-in calling feature so that you could yell at your buddy for playing Qi, knowing he has no clue what the word actually means? Who knows – pretty soon the option may be available.

Twilio (News - Alert) released its native SDK for iOS last week, giving iPhone (News - Alert), iPad and iPod Touch developers the ability to load a fully functioning VoIP phone into any mobile application. While the SDK is probably aimed more at developers of call center applications, the VoIP calling feature will surely make its way into some gaming and entertainment apps as well.

With the Twilio client, developers can build apps that allow users to instantaneously connect to a Twilio or standard number while remaining in the application. Think about the native IM feature embedded into mobile apps but with the added component of voice. Twilio made this capability available to website developers some time ago but had yet to roll out the SDK for mobile innovators.

TechCrunch, which got an in-depth tour of the SDK from Twilio, said that we can expect to see loads of call center apps that enable agents to go mobile with just a headset and an iPad. Agents can have access to rich CRM data while they remain connected to a customer over 3G or Wi-Fi.

Other apps headed your way will include mobile conference calling software, travel apps that connect you right to a reservation desk and – you guessed it – voice-enhanced mobile games, says TechCrunch. Adding to the fun is Twilio's online presence feature, which lets users know when any of their contacts have the app open and are available for a chat.

Inter-app VoIP calls should only cost around 1/4 of a cent per minute with Twilio. The only question for developers is if they should eat the cost themselves or pass it along to the user. And if so, how.

The demand for VoIP calling applications – and the VoIP market in general – was a major topic of discussion at ITEXPO East 2012, which just wrapped up in Miami. For a more in-depth look at the VoIP market, check out the interview below with Corey Potts, VP of Sales at VoIP Innovations (News - Alert), a wholesale provider of VoIP services.

Potts highlights a number of topics in the field and details the company's own mobile app designed to allow ITSPs to manage their own VoIP account while on-the-go.