Backup would be either telephone or cellular. There are whole house monitored systems out there, or you could roll your own, and just monitor through sensors at the home, that would update you.
Costs are more for the long term, on the systems that you would put together on your own, vs going with a package, that would be monitored by a company.
I use Our home spaces, for my ted5000 & 3m thermostat, with their radio in the thermostat. Their software for on the go, on works with the iPhone, but you can access through a web browser.
Ecobee thermostats allow for modules to be added, so do prophilex thermostats. Smarthome.com has pretty much every monitoring gadget on their website.