It's wider than just bilateral agreements about passports, but so much depends on whether the rUK negotiating stance is more jilted lover than supportive older sibling. Salmond is obviously expecting, nay demanding, the latter, on everything from currency to energy and easing EU membership. Whoever succeeds Cameron after he's sacked for breaking his country may well be so pissed off at the vast amount of time, money and opportunity cost this will take they'll force Scotland to argue about every DVD and saucepan and expect all their mates to unfriend it on Facebook.
Without huge support from rUK (or maybe someone else) the Scottish foreign service will need to establish consular representation everywhere its citizens want to travel. From day 1. If a couple of them get murdered on a beach in Thailand, kidnapped in Syria, nicked for smuggling in Columbia or just seriously ill in Kentucky they'll need a consular machine ready and capable of swinging into action. We take all that for granted, just as we take passports, Ehic and the foreign validity of driving licenses for granted. Scots will only be able to do so once all those bilateral agreements have been made, polished and ready for use on day 1. Or if big sibling rUK provides facilities, countersigns the paperwork, guarantees good behaviour etc. I can see May or Gove or whoever wanting to know what's in it for us.