Finally getting my brain in to the GENOME Midi Sequencer, by White Noise Audio. It is VERY COOL!
Using network MIDI, I've connected the iPad2 (running Genome/Arctic Keys/BS-16i/NLog Pro), to an iPhone 4 (running Sunrizer) and an iPod Touch (running Arctic Keys).
Also, via an iRig MIDI connector on the iPad, am sending a MIDI signal to a Moog Little Phatty as well. Can you believe this all works! I have a pretty strong WiFi signal, so the iPhone/iPod Touch work well and there isn't any discernible latency.
Presumably I could run my other iPod touch as well, with a compatible virtual MIDI app. I also have a MIDI splitter box, so the idea of sending to more MIDI hardware is also a idea (or by chaining with MIDI THRU).