PS: Cortex can work with xAP. of course, and Kevin a while back was having a go at getting display options working on an O2 Joggler - not sure how far the project got, though (ISTR some problems with Flash, and the amount of time it was taklng) ...
for the moment, we have just one (numerical) display being fed by Cortex - too expensive to use in other locations, too, though, and not sure it could show the time (we use it to context-sensitively show temperature & speed & other such) ...
still, as you imply, given what you're thinking of, we could maybe use redundant old iPhones and/or iPod-touches to do all this (currently, we use them for watching recordings & keeping an eye on TV News, using EyeTV, and as calculators, using an HP41 emulator app) ...
anyway, wonder if xAP gives / could give a route to what you're looking for ... ?
the effort needed to integrate all this together, in the IoT world, will be enormous, but many hands will make light work ...