Just discovered this app on ios which is currently free premium unlock. Seems like a great way to extend the sampling capabilities of the Digitakt. It does support midi mapping so you can use the midi tracks (encoders and all) on DT to control the app. The sequencing workflow doesnt seem to be very intuitive in the app itself right now, but thats no issue when using the DT as the sequencer. Should only require a usb cable to be connected for audio and midi. It even supports AUV3 (unlike Koala), so you can host synths or other plugins in it. What also is interesting is that I found an option to turn off anti-aliasing. Quite unusual to be able to choose this for yourself no?
DAWNBEAT is free and the Premium Unlock IAP is currently FREE! Usually $4.99