More of the multi-year NextGen initiative is about to go live. Arguably the key piece of the entire plan is the ability to make ride reservations even before the vacation begins - the part called xPass internally - and it's about to start tests with the public. Called "FastPass+" (pronounced FastPass-Plus, like Google+), the full details aren't known yet. What we do know is that early May will see a random selection of visitors to Disney hotels receiving an invitation to participate - it certainly won't be everyone with a hotel reservation! - and they will indeed get to select ride times ahead of their trip.
They will use a device with RFID. Early tests of this technology at the Epcot entrance gate were a Mickey sticker pasted on the regular day pass, or a separate card could easily be possible. The advance word was that wristbands (think Lance Armstrong's Livestrong) would be the "card", and visitors would just swipe them by bringing them close to the readers.
The readers were put in place over the last week or so in the Magic Kingdom. All rides with a FastPass system now have them, as well as a few others such as Haunted Mansion. The FastPass+ system depends on *adding* rides to the system, so that users holding reservations are more spread out.
The readers are hidden under canvas, so we haven't seen them yet. But there's a large ball at the top of the post; that much we know by touching them.
Update: Paul Lalli provided this image of the Big Thunder scanner, taken on the first day of testing (May 1):
Kevin Yee is the author of numerous independent Disney books, including the popular Walt Disney World Earbook series and Walt Disney World Hidden History.