The HM does have the ability to use a wireless probe (a single probe), but I don't think the design has ever been finalized, particularly the grill side interface. I think it can be done though (Bryan has one) if you want to experiment.
I had suggested that perhaps a good way to design a wireless system would be to use two HM boards with wireless boards on them to allow them to communicate with each other, then populate the grill side board with the probe and fan hardware, and populate the other (controller) HM board with the hardware to communicate with the rPi. I passed this idea on to Bryan and he has considered it, but he is the one that would have to code it and so it's one of those things that are on the to-do list, or perhaps the to be considered list. So far I haven't heard anything about it actually happening but HM development keeps marching on, so who knows, maybe one day it will happen....