Interesting questions!
I have not seen any publicly available SDK or API, the only current connectivity is with Alexea.
How do the other systems deal with open window detection? Apparently this TRV does do open window detection but i dont know how or if there are any alerts that its detected an open window.
Cycling of TRV's not sure, but again they could stick that in the app to periodically cycle to TRV's?
Its all made in Britain..not sure if that's an bonus for the system!
Open window on Evohome works by detecting a sudden drop in temp, this can be adjusted for both drop and rise in temp within the trv menus. I get a symbol appear on the trv and the controler if a zone enters this mode, where it switches heating off for a set period or until the next scheduled change.
I think as time goes on that Wiser could be the best value setup. I would miss the extras though, for instance remote thermostats and for the bathroom the underfloor actuator instead of a trv.