Call Recorder for Skype is a new Cydia tweak that lets you record and save voice calls made on Skype and save them on your iOS device. You can then transfer those saved audio files to your computer from /Applications/

This doesn't come cheap though costing around $6.99 from ModMyi repo but expect cracked versions soon enough.

Anyway I don't really see the point in this as most people use their PC/Mac client for this and unless you need some sort of business call or some shit it's basically useless.

*thanks to ijailbreak for dem info