Thanks for useful replies. I agree that a local box for identification/authentication may well be the answer, and not overly complex or expensive. I will also look further at the Exosite.
Incidentally, so far I have found the CC3000 + MRP430F5229 relatively straightforward and reliable, but then I have just spent a whole lot of time trying to use the Roving Networks Wifly, which I found expensive, difficult to set up and very unreliable. (I have also tried zWave, which struggled to communicate from one room to another).