zwave supports 2way communication at the protocol level. depending on the series chip it will support instant update status of changes. if not, most software uses a polling method for periods of time (i.e. poll all device status every 30 seconds). the protocol does support acknowledgements of commands sent and some of the newer usb sticks support silent acks.
zwave is made up of 'command classes' at the control level. these classes describe the type of module to be control as well as any methods to control them. there is also a general basic command class that covers general overall commands, including some thermostat commands.
i do not develop in linux but for anyone who does, the easiest way to have most of the classes right now without buying the development kit is to use the leviton rzc0p (that's zero not o). it is a serial zwave device that maps ascii code to zwave commands. i am sure anyone who is developing linuxmce would have no problem writing the code as long as they can develop a linux driver for the rzcop. leviton has all of the documentation for the ascii codes also so as i said this part would probably be a piece of cake for any serious developer. i would definitely look forward to seeing it implemented.
i have seen 1 zwave box on the market that looks linux based, the hawking homeremote. if someone could reverse engineer this box it might prove fruitful in porting it over.
on the windows side i have personally controlled the following to date via zwave:
1. lighting - switch, dimmer, battery operated dimmer controller, garage door opener with lighting control built into keychain
2. plugins - lamp dimmers, 15amp appliance modules (indoor and outdoor)
3. motorized window shades
5. motion & door sensors
6. receptacles (outlets)
7. screw in lamp module (good for basements, laundry rooms, & torchlamps)
8. controllers - handheld remotes, a/v remote (harmony 890), 4 & 5 button wall controllers (control any 1 or more module on 1 button, not just lighting), appliance box (hawking), windows software (wmc, web page, wap page) via usb stick & rzc0p, java applet for cell phone (moshi)
speed on the newer devices is up to 40kbps and they are working on a chipset for direct IR replacement with RF in the future.
also controlthink.com sells a 40kbps firmware updgradable usb stick if developers want to go that way.
hope this info helps anyone who is looking to further the development of zwave in linuxmce.
i have some basic videos showing some of this stuff at www.idesignsgroup.com
. check the 'gallery' link and click the red down arrow twice to get to the home automation section. click the videos to play. enjoy.