From what I gather, this 'wireless monitor' or iScreen would be about the size of a Tablet PC but will have no processing power other than monitor hardware and a wireless transceiver. It's also purported to come with a detachable keyboard but no battery (now that seems odd). It's unknown whether the iScreen will have handwriting recognition or not -- though I suspect it makes sense to include this feature to better compete with Tablet PCs.
So, this thing would be a wireless terminal in the form of a flat screen monitor. If you're an old-timer like me, you might remember that old mainframes followed this concept of a central computer CPU with multiple 'terminals' with access. It's unknown whether more than one iScreen could use a single Macintosh or not -- I'd guess it's a single iScreen per Mac .
Even though this is all speculation, the idea of an iScreen with optional detachable keyboard intrigues me. Rather than hauling a laptop around the house, I could just take the screen. Since there is no CPU on board, it's possible that battery life might be quite good compared to a laptop or Tablet PC -- assuming there is a built in battery.
Of course, these kinds of rumors about Apple device often lead nowhere, like the long running rumors of a mythical Apple PDA which have never surfaced in real products. This could also be a Wi-Fi or Bluetooth wireless monitor you can hang on a wall or even a well-placed leak by Apple to divert attention. Still, a wireless monitor... that seems more in line with what Steve Jobs might consider a killer consumer device.
Here's to hoping for an iScreen! ;-)