This neat little (but surprisingly complete and professional) tool is going for a couple of dollars on ITunes (link).
Unfortunately this appears to be an ipad exclusive, limiting the audience somewhat. But if any of you happen to have access to one i would definitely recommend this.
(personally going to be using this for a couple on current projects)
It has a crisp interface and a great retro sound, with flexible export options (dropbox/email) and a tweak-able synthesiser this isn’t just a toy.
(plus it’s two bucks)