If you have some of the Power Functions remote control stuff, here is a way to get the remote control receiver to serve as a sensor for the NXT, so that you can wirelessly control your NXT robots, using only LEGO parts and NXT-G. The example shows the NXT responding to the up/down/center position of both the red and blue controls on the remote control by drawing graphic arrows on the screen to indicate which way the controls on the remote are being pushed.
This solution is a kludge. It requires several expensive and heavy LEGO electrical parts, and also requires the Education version of the NXT-G software or the Legacy Block Library add-on, but it's all snap-together with LEGOs with no external hardware or software, so if you happen to have the parts already, then it's easy to get it to work.
I am showing this mainly to call attention to a question: There are apparently 3rd party IR Link sensors available for the NXT now (and a couple of nice home-brew ones have been demonstrated), but does anyone want to offer an opinion about whether there is a solution out there that is friendly enough for kids to use with only NXT-G? Note that I am not talking about controlling PF motors from the NXT, or just powering the NXT motors directly from the PF stuff(which can be done with LEGO's adapter wires), but rather giving wireless PF remote control input to your NXT-G program in an easy and reliable way.