Which wifi repeater to buy that can be OS X configured? I need to extend my Wi-Fi and would like the type that just plugs into the mains.

I cannot find a repeater or extender that does not use Windows to configure.

Is there a repeater or extender which can be configured with OS X?
You can use Apple's AirPort Express to extend wireless networks. This can be configured from AirPort Utility in OS X.