I have also been looking for this, too cheap to pay for voicemail and google voice isn't available in canada. If anyone developed one I'd buy it, theres one app in the play store but it doesn't work with qualcomm devices:/
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?