I have an RCX and want to know if it's possible to connect it to an iOS device. If this is possible, how do I do it?
Communication with the RCX Brick was via the Infra Red tower (or IR Remote Control) which connected to the computer with either a serial or USB cable.
As neither iPhone nor iPad have an IR port, there's no way to connect directly between the two.
You might be able to do something with a docked iOs device, but that strikes me as somewhat pointless.
You could do it using a computer as an intermediate. Basically, you have a wireless connection between your iPhone and your computer, then the IR link between the computer and the RCX. It would be technically challenging but not impossible. The IR tower uses a serial port and the protocol is detailed here http://legolab.daimi.au.dk/CSaEA/RCX/Manual.dir/RCXManual.html. The connection between the computer and the mobile device could simply be achieved via wireless connection using TCP sockets and wouldn't have to follow any very specific protocol at all. All of this could be achieved with any number of programming languages, but Python and Visual Basic would likely be the easiest. I could help you write the software to do this if you are very determined, but I only have experience with Windows, so the computer itself couldn't be a Mac.