I don't really see the iPad as a DCC controller. Maybe if you wanted a dispatcher's panel or something similar, but it's too big to be handheld with one hand and operated with the other while you're walking around the layout, and do you really need the larger screen for a throttle? Most hand-held throttles are fairly small.
The iPhone is a much better form-factor for a handheld controller (not surprising given that it was designed to be held one-handed), and my only objection to the current DCC app,
WiThrottle, is the lack of turnout control. I already have JMRI and a LocoBuffer on my Zephyr, so adding the wifi link to use either would be fairly easy.
Of course, if someone came out with an App that would do a dispatcher's panel and throttle on an iPad, I'd probably change my tune. It's the perfect excuse to "need" an iPad...
The pad is designed so it can be held in 1 hand like you would hold a clipboard, and use it with the other hand, like you would write on a clipboard. That doesn't necessarily mean it's a good device to carry around the layout the whole time though.
We've already talked about a throttle app for the iPhone/iTouch, more about that here:
http://www.jnsforum.com/index.php/topic,1729.0.html . As mentioned there, the basics are up and running.
The problem with any app for iPhone/iTouch/iPad is that it in most cases still needs a computer with software on it that controls the layout. Right now, only the JMRI software supports an iPhone/iTouch app to use as throttle, but at $9.99 it's FAR too expensive for what it does. Also, JMRI on OS X isn't the best. Java makes it slow, and on top of that, the serial port drivers JMRI uses are only compatible with 32bit Java. Not that much of an issue, you can set the default Java to be 32bit, except that every program using Java will then use the 32bit version.
On a more personal note, I think JMRI and WiThrottle are too ugly to even consider using. There's already tons of ugly hardware throttles around, why make the apps even more ugly? =)
If you have a Marklin CS/CS2 or ESU ECoS, there's TouchCab. That's an app that connects directly to the central without needing a computer. Obviously it's useless if you happen to have for example a Lenz or Digitrax system. Also, while not quite as ugly as WiThrottle, TouchCab is still ugly. The good thing though, it's cheaper and there's also a free version. (I believe the paid version can also do turnouts etc)
As for the iPad, it would allow for a couple of things that won't work well on the iPhone/iTouch. The most obvious is of course switch boards/dispatcher panels. The iPhone/iTouch screen is just too small for a switch board to be useful. On the iPad however, you can easily have multiple nicely detailed switchboards with the ability to control turnouts, signals and more.
Another option is to have 2 throttles side by side, 4 smaller throttles in a square, or even a list of mini-throttles which give an overview of which trains are running with which speed/functions and (in case of a block system) where on the layout they are.
Then there's waybills and the like. It seems many Americans love simulating a real railroad with their model railroad, so you can split the screen into a throttle on 1 half, and a waybill (and other info) on the other half.
If you have a camera equipped train, you could stream the video to the iPad, and have a throttle below the video, that way you can control the train as if you're the train driver (possible on the iPhone/iTouch as well, but very limited because of the screen size.) Add a dynamic braking system and it could actually be quite interesting.
Of course, all of those ideas need server software that on 1 end controls the actual layout, and on the other end communicates with the iPhone/iTouch/iPad. I'm slowly working on something like that, but it's going to be a while before anything usable is done. On top of that, it'll be for OS X only. Of course, there could be a windows version, but someone else would have to code that ;)
