I don't want to link-bomb this thread but if anybody's interested, I've made a controller panel for the cheap TB Midi Stuff app on the iPad.

It would be no problem to convert this panel to sending NRPN messages instead of SysEx, but to be honest I don't see much of a point - you may save a couple of MIDI bytes in transmission but internally, the same code handles NPRN and SysEx parameter changes.