US iPhone users will soon be able to access multiple applications while using mobileVoIP solutions.The Line 2 mobile VoIP application will take advantage of the new multi-tasking feature available on the latest iPhone operating system - iOS4.This will enable customers to open up other applications, such as a calendar, during a VoIP call.Peter Sisson, chief executive officer of Line 2 developer Toktumi, confirmed that users can make calls over Wi-Fi or traditional mobile networks. He said: "Although the current version of Line2 still allows them to receive calls when the app isn't running, they come in over cellular. "Now people who don't have cell reception or are trying to reduce their cell minutes can get their calls, even if they are listening to music or playing a game."Customers will benefit from improved sound quality, while bills will also be reduced as call minutes will not be used as frequently. The new iPhone operating system will be launched on June 21st.