It wouldn't hurt my feelings at all to be able to let some device or app in my world slurp up information about how much power the fridge is using, squawk if the door's been left open or something has failed, etc. If the compressor is running longer or harder than usual or the icemaker is reporting a jam or water flowing in an unusual way - getting an SMS message from my home network about something like that while I'm out of the house could actually head of a real mess. But all of that can be done via a well-supported, locked-down home controller (say, a Vera product) that chats with the stuff in the house over the meshed Z-Wave protocol and stays off of the wifi network. Z-Wave is great. You bind a device to your controller, and that's it - the war driving kid from next door with some Z-Wave sniffing widget might be able to see it's there, but he can't take it over without physical access.
Our home controller is, itself, wired to one of our local network's DMZs and doesn't use wifi directly. So long as I run a decently maintained firewall and APs, the presence of Z-Wave based devices around the house (current count ... over 20, mostly lighting but also fire/CO-detectors, motion sensors, and some controlled outlets) isn't something I worry about. If my internet-facing network is compromised, I've got different, bigger worries.