Sean Kovacs released GV Mobile App via Cydia for free on jailbroken iPhones
Apple had pulled the plug off the official Google Voice App and also the GV Mobile app that was based on Google Voice service. Now, the GV Mobile app developer Sean Kovacs didn't prefer to take the app to mobile Web. Instead, he released it for free via Cydia, App package management interface available after jailbreaking the iPhone OS based device. Apple was worried that Google Voice App and GV Mobile app mimicked features of iPhone and hence, blocked them.
Sean Kovacs' GV Mobile app is not an official Google Voice App but merely makes use of Google Voice service. Kovacs released the GV Mobile v1.2 App on Cydia with a promise to roll out update in few weeks. Apparently, Kovacs has enough of grumbling over Apple's walled garden and decided to offer the app for free.
So this app is available from Cydia for free but first users have to jailbreak their iPhone OS based devices using the redsn0w tool. Jailbreak is a reversible technique. Beware, jailbreaking the iPhone OS based device voids Apple warranty.
Not all apps can make it to Apple's App Store due to stringent rules and vague policies. In those cases, Cydia Store is a viable option for individual developers to sell their apps.