Do you wish that your iPhone 4 has some 4G speeds? Current rumors suggest that Apple won't be hopping on the 4G bandwagon for the iPhone 4 (and really, the state of what's called "4G" in North America is pretty messy right now). But if you must have 4G speeds and you happen to live in Korea, then it's all possible on your iPhone 4.
Korean Telecom has introduced an Egg sleeve that accommodates an iPhone 4 and acts as a battery extender as well as a WiMAX data radio add-on. The extra 1500mA expansion battery will give the iPhone 4 and the WiMAX device five full hours of 4G surfing.
It's not exactly the most compact solution; but at the equivalent of $120, it won't break the bank.
As Engadget points out, U.S. iPhone 4 users who want a faster data network can use Sprint or Verizon's "4G" mobile hotspots.