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“Gell”… this is quite a useless word.
“Gell”… in Swiss or southern German this is just an interjection.
Just to reinforce something which was said before.
Something like “do you like it, DON’T YOU”? Or something which sounds like “RIGHT?”.
Basically a rhetorical question!
But when I hear such interjection after a salutation like “ciao” I start laughing: It is like confirming (to yourself, maybe!) that you greeted someone in a proper way!
Why the hell do you need to confirm something after the word “ciao”, which is probably one of the most international and known all over the world?
Please read my post! OK, GELL?!
Real Swiss 
You say that gell (after ciao) is used as intrejection in southern Germany or Switzerland.. OK.
In Italy sometimes , without any sense we say: Ciao, bellezza .
I think that in many Countries there are , after Ciao, interjections with no sense at all.
M.G. Cinisello
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