https://soundcloud.com/tjam
One thing that I want to say to is that there is a full free version for PC / MAC that comes both as a standalone and as a VSTi. WEJAAM is the only app that comes as a VSTi as well (with the exception of Heat synthesizer but your device has to be connected over wifi to use it in your DAW...) and think that is something that is very helpful for people that work a lot in a DAW environment.
Have not played much with WEJAAM but the little I have it has been a nice Groovebox type of experience.