Wi-Fi over Coax
Back in the day, almost all cell phones had a miniature coax port on them.  They were "hidden" in that you probably had to pry off some nondescript part or open the battery cover up or something.<p>This is how we tested mobile networks.  It works great.  The only problem is when someone forgets to make a tight connection or attach a signal attenuator.  Since the first thing you always test is emergency calls, once in a while your call ends up on the real mobile network and the fire department shows up in your parking lot.  This happened about once or twice a month where I worked.  They knew what our business was so they were never mad at us, but we had to pay a fine each time.