The audio-jack based interface is very clever- the whole package is wonderfully simple and straightforward. I hope that mass production can bring the price down a bit, though.
Making a "real" iphone accessory through the 30-pin connector is simply not possible for hobbyists/small outfits. This also makes their communication interface with the robot somewhat portable. I like :D
If anyone's interested, there _is_ now a way to interface RS-232 devices from an iPhone using an Apple-approved cable:
http://www.makershed.com/ProductDetails.asp?ProductCode=MSRP...
From what I've heard, negotiations with Apple took a lot of time and were quite "complex". Also, the cable unfortunately costs 80$ (because of the custom, "secret" DRM chip enabling the interface). Which goes to prove that the audio jack goes a long way!