LSMusicSeek

Cydia crack's | ipa crack's | jailbreak has posted a new item, 'LSMusicSeek'

Replaces Lockscreen volume sloder with a seek slider for music playback.
Cydia Updates – via planet-iphones.com

You may view the latest post at
http://www.ihackstore.net/2013/05/01/lsmusicseek-2/