Hi,
Here's a great idea:
http://protocolbrickz.com/
Offers WiFi, ZWave or 4G/3G, and an SDK is available. The only question is will they offer US and EU Zwave frequencies, as they appear to have been developed here in AU.
Already one product has been develoioped to utilise these,:
http://sockitz.com.au/m/index.php/sockitz-usb-power-points/all-new-glass-connected-touch-sockitz.html
Indigo support for these would be great!
Mclass