Hi Kalle,
I did see your post about your wrist adaptation of a wifi headset: stellar Idea! After reading your post and a few others linked to the James Lipsit Website where he uses the HAL2000 controller with very expensive Shure microphone set up for whole home control. My idea lies somewhere inbetween wherein you have the permanently installed mics around the house (or at least in the areas of interest of having voice control) but instead of the expense of the intelligent Shure backend equipment and HAL2000, the mic circuits could be toggled on and off with a relay on the lighting system (in this case a Lutron RadioRa2 system) and the VOX could be active listening or ignoring on the same commands that toggle the mic relays. This could be achieved using the small RF pico controls mentioned. The come with a "car visor" kit to add a clip that could be for your pocket or belt, a table top pedestal mount and the option of mounting on a wall with or without a faceplate (with a face plate is appears as any other light switch, but without a faceplate it is easy to remove and replace on the wall so you could "grab" it on your way into a room and replace it on your way out, giving it a "place" when you are looking for it).
There is an out of the box relay solution called a VCRX that integrates wirelessly with the Lutron system that has 6 keypad pushbuttons, 3 CCI inputs and 4 CCO outputs that can be programmed in the Lutron Software. Not perfect for everyone I will admit as Lutron can be expensive in it's own right, but that is the business that I am in. One thing for sure is that the Lutron RF technology if within proper working ranges is one of the most stable and bullet proof systems.
here is a link to the VCRX:
http://www.lutron.com/TechnicalDocumentLibrary/Visor%20Controls_369-224a.pdfyou will notice that one of the inputs is labelled as a security input. it is possible to wire one of it's outputs back to this input to achieve something like: Yell for HELP and have VOX activate the output, the output activates security mode and you could have all of the lights in the house flash off and on (including the outside) and send a contact closure the security system.....