Volume Amplifier is a jailbreak tweak that boosts the iPhone’s volume to 200 percent, which can come in handy when talking to someone on the phone and the voice on the opposite end isn’t audible.

The tweak was recently updated for iOS 8. Volume Amplifier directly manipulates the audio stream rather than messing around with system config files, and hence works similarly with the earpiece, the speaker as well as headphones.

While you’re on a call you can simply use the the volume up/down buttons like you normally would, except that you’ll notice a new overlay and that the volume goes beyond 100 percent. It works with the speaker and earpiece on iPhone 6, iPhone 6 Plus, iPhone 5s, iPhone 5c, iPhone 5, but only with the external speaker on the iPhone 4s. And it works not only for phone calls, but even for VoIP apps like Skype, Viber as well as music, radio apps etc.

Note that by increasing the volume above the recommended limits, you may damage your speaker, so proceed with caution before installing the tweak. Volume Amplifier is available for $1.99 on Cydia.

http://youtu.be/OI3rYzvGhBc