Sorry for bumping this old thread, but it was the only one that came up for wireless. Hopefully this mod isn't already posted somewhere else.
The new W21 / W22 wireless bits seem to have a Channel Select function, which I guess is to allow multiple transmitters to work in proximity and be linked to specific groups of receivers.
The RFD21733 radio module used on the W11 / W12 bits has several modes. It can be used to send digital controls (like for garage door control) or serial data (at about 9600 bps I think). The data is bi-directional which is cool, because with a little modification, the W11 / W12 combination could be used to send controls and data in both directions.
As used in standard LittleBits modules, all transmitters look the same, and all receivers look the same. That means that one transmitter can control multiple receivers, but you can't reliably use two transmitters close together because the receivers can't tell them apart.
This youtube link shows my mod:
The standard mode used by W11 & W12 is mode 2. Mode 3 is identical, except that it requires a receiver to 'learn' about each transmitter before they communicate. This makes a very easy to use and flexible wireless solution.
Modifications can destroy your littlebits modules. Don't even think about it unless you are confident working on this kind of circuit board.