Using the DCE approach on the iPhone would be nice.... and make for a very nice, fast UI, that's retargetable, etc. However, it isn't just a matter of a few DCE messages, we are talking about a _lot_ ... there are thousands of different messages you can send or receive (commands and events), many of which would be needed to implement the Orbiter on iPhone... and in addition you would need to implement the entire Orbiter UI engine so that all the screens can be generated for it and then it can read these and display them on the device.
None of this is a small undertaking, and really does an iPhone specific Orbiter need to be _that_ retargetable?! By all means, I would like to see such an Orbiter, but compared with the "standard" method of building a Mobile Orbiter which is just a small piece of code responsible for receiving PNG images over RFCOMM/BT and sending back button presses/screen touches, the standard method would be a much shorter learning curve for you and very much quicker to implement! Perhaps start with that, and once you've learned DCE and the screen generation functionality a bit more, move on and implement the "smart" version?
Its also worth noting, that although building a "full" Orbiter for iPhone (or any other device) dealing with DCE messages is a big ask... there is nothing stopping someone using DCE messages over WiFi on such a device to trigger simple tasks... that would be very easy. In other words some simple, preconfigured tools for triggering specific DCE messages, not an Orbiter at all... that's the beauty of DCE, an Orbiter is a rolls royce example of DCE usage, but it is the DCE system that is doing the clever stuff, and you can hook into that using simple DCE commands (perhaps an iPhone app that you install and preconfigure with a couple of lights, so that you can hit the app and turn on an off a few lights around the house, etc) ... porting messagesend would be a good start