Basically the same question as the locked Wifi router that has a button to turn wifi signal off? or Wireless router (or AP) with hardware on/off switch for WLAN from wirelessfourms.org in 2007.
My wife found Is Your Health on the Line which seemed like a little too scare tactic about the dangers of RF energy, but suggested you turn off your router when not in use. Let's not debate the dangers of RF, because that appears to be what got the previous question locked.
I have hard wired devices that need to be connected (e.g. TiVo), so I'd like to find a wireless router that has a physical off switch for the wireless network. Other possibilities are to block the signal by putting a tin can over the antenna or disable the wireless in software on my existing router, and buy a second device for wireless which can be unplugged. Since my existing router is a circa 2003 Dell TrueMobile 2300 Wireless Broadband Router, I could probably use an upgrade.