Wifi signals actually create fairly complex regions of nodes and nulls in most rooms. There might not be a simple gradient between the two rooms in this setup, so it could be difficult even if people really were "sensitive" to those signals. It would be more reliable to just turn the router on and off and (in a double blind test) ask "sensitives" to tell you if the router is on or off.

That being said, blind-folding a bunch of these people and asking them to simultaneously stumble around and find the router would be pretty hilarious.