So I am visiting some family in Perth for Christmas and then spending New Years in Sydney. I have a jailbroken US iPhone and I plan on installing ultrasn0w before I leave on my trip. I have a couple questions about using my iPhone 4 while visiting and I would appreciate any input. 1) Do any carriers sell prepaid SIM cards (micro or not) that will work for data on the iPhone while I am visiting? I plan on running skype or fring or google voice in the background so people can call if necessary and I am also not disconnecting from home/work. 2) Are these prepaid data plans expensive (I don't care about voice since I may use it once or twice)? 3) Is there a difference in terms of coverage between carriers? I would love to get a SIM card before leaving here, but I am sure the Sydney Airport has a few places I can grab one. If there are not any prepaid data plans then I may rent and XCom Global mifi and carry that, but I would like to carry a minimal amount of devices. I went to some websites of the carriers (Optus, Vodafone, Telstra...), but couldn't find any good answers there, so I figured to ask the knowledgeable people of MacRumors. Thanks for any input guys.