http://www.screwfix.com/prods/76975/Hand-Tools/Detection-Equipment/CED-Plug-in-Socket-Tester
this is the one i own and it detects:-
-CORRECT
-NO EARTH
-LIVE & NEUTRAL REVERSE
-NO NEUTRAL
-LIVE & EARTH REVERSE
-LIVE FAULT
by using a combination of 3 LED`s this is just a basic tester...