In case you have missed it like I did, HiTechnic has introduced a new Sensor Multiplexer. You can add any HiTechnic or Lego supported sensor. This is in addition to the Touch Sensor Multiplexer.
It looks pretty cool, and they claim you can have multiple multiplexers on a single NXT, so you can have up to sixteen sensors on one controller (WOW!). Throw in an IRLink to control some PF motors and an RCX and you have incredible power and control from a single NXT.
I already have several HiTechnic products and I find them to be very reliable. I have contacted them about technical support and they are great and usually get back to you quickly.
The drawback I see is that there are no NXT-G blocks to download yet, but they will be supporting LabVIEW 2009 and RobotC soon.
Now where did I put my wallet.....