If im correct the controller runs on bluetooth. The only major potential problem i see there is that it may be susceptible to a crowded spectrum issues.
Last week me and a friend ran a small stress test by game sharing on PSP, sending data wirelessly to my phone via bluetooth and downloading to my PC wirelessly and all three ran slower than usual. All three were within 1m of each other so thats probably why, but it still potentially can cause effects elsewhere at a bigger distance.
I'm not sure if it will cause a problem for Wii, and i doubt it given it's working at a distance, but being in a crowded wifi zone might affect it a little. Lucky for us the nearest wifi zone aside from here is a phone box, but then there are places like Canary Wharf (and soon the City) which is completely blanket covered with wifi (and subsequently is completely covered in nintendo wifi stickers).