Money is an imaginary concept...you have to believe that a piece of paper or cheap metal amalgam has a value.
It would be relatively easy to create an independent currency...all you need is a template, a row of printers and a stack of paper bought from the local stationery box on Sauchiehall Street. The hard part is getting Angus McPublic to believe that the currency has a value, didn't anyone notice that the 'i promise to pay the bearer' strapline has vanished from our own notes...(incidentally along with the gold reserves that were supposed to be paid by the bank if you wanted to exchange said piece of paper for something of tangible value)...the piece of paper in your wallet, is just that..a piece of paper...a promissory note from the bank to give you the value of it in gold, bread or mead.
Anyone been down to Lloyds/TSB to ask recently? My guess is you'd get a better deal trading the pieces of paper for goods at Tesco than trading them with a banker
Anyhoo..Scotland would have to hornswaggle the EU and every single trading partner it has, that the value of its oil, fishing and tourist industries are of enough value to make it's promissory notes a valid premise. (Good luck with that one Alex mate)
You also need to consider that the rest of the UK has as many tendrils in Scottish society as Norton virus killer has in your average desktop operating system, they would need a complete reformat, and Alex Salmond is not offering that as an option, he is picking and choosing, playing to the bravehearts and Rab C Nesbitts.
Personally I dont care one way or the other, although I do think that if they left the UK the Scots would have a very tough time of it for the forseeable future, Salmond cannot deliver on his promises..but hey, when has ANY politician ever delivered?