This may be an obvious statement, but iFly cannot listen to both at the same time. These devices effectively set themselves up as an access point (hostapd) and most tablets / phones only have a single wifi chip so they can only connect to one network at a time.
I'm not sure if these devices (or iFly for that matter) supports bluetooth, but in theory you could connect one to one via wifi and another via bluetooth.
<Peter dons his tin foil hat> Just make sure to wear your lead underwear to protect yourself against all the RF :) <Peter removes his tin foil hat>