Kentai has released iPG-800 – a MIDI Controller iPad app that emulates the functionality of the PG-800 Synthesizer Programmer that was built by Roland. It only works with a Roland JX-8P synth or a MKS-70, the rack version of the JX-8P.
iPG-800 is a CoreMIDI app and connects to CoreMIDI compatible MIDI-Interfaces and to wireless MIDI Network sessions.
See the Kentai site for details.
iPG-800 is $4.99 in the App Store.