Bolt is a small, distraction-free VoIP calling dialer app replacement for Android

Even worse, all your friends use different apps, and staying in touch with everyone means keeping several apps listening for signals at once, which clogs up your device. It also means launching a different app depending on who you want to call or chat with. The folks at Bolt saw through this and chose to walk against the grain. Bolt is a VoIP app that functions as a simple, distraction-free dialer replacement. It integrates with your phonebook in the same way your stock dialer does, but there's an important difference. Calls to and from contacts that don't have Bolt installed will be routed over your regular wireless network and charged accordingly. Calls to and from fellow Bolt users run through your data connection. No app juggling, no sticker packs, no memory hogging. Just sweet VoIP calling, the way it should be. 

The developers claim Bolt compresses voices into just 60KB of data per minute, which means you'll get a whole lot of call time regardless of your data plan. Fancy what you're seeing? Bolt is free, but it's only up for Android right now. The eventual iOS version will be released when it's done.