Sahlene (Estonia 2003 - Runaway) - Swedish.
Celine Dion (Switzerland 1988) - French Canadian
Englebert Humperdinck (UK 2012) - Indian
Yep - and further back Gina G (1996) and Olivia Newton John (1974) were both Australian.
And then you've got some performers who have represented more than one country. Elisabeth 'Bettan' Andreassen who was born and brought up in Sweden to Norwegian parents, and has performed at the ESC 4 times.
Once in 1982 for Sweden, and then three further times for Norway (1985, 1994, 1996) and has entered Norway's MGP 5 times, and Swedens MF 6 times. She's hosted both MF and MGP I think...
As for songwriting - I don't think there is much of a national rule these days is there?
Thomas G:Son and Peter Boström (both Swedish) were involved in non-Swedish entries each this year weren't they? (Sweden, Norway, Spain and probably a few others) Fredrik Kempe (Swedish) has written entries for Sweden and Norway in previous years. Last year's Azerbaijani entry was written by Swedish and UK songwriters... (And had Swedish backing singers - Shirley's Angels from MF 2011 minus Shirley, Swedish choreographer(s), Swedish hair and make-up etc. etc.)