Hardware

Raspberry Pi : model A (no need for wired ethernet)
Wifi USB key
Bluetooth USB key
Powered USB hub (used as power distribution)
I2C Servo controller PWM card
relay control card
temp/humidity sensor
smoke sensor
Pi camera
IR movement detector

and currently it looks like this:

Central hardware : initial thoughts

For the central unit, it needs to be able to:
 - connect to networks : wifi or a national M2M network (eg Sigfox)
 - communicate with the user via voice/audio : microphones, speaker
 - lighting/moveable elements for personality : servo controller/LED control
 - monitor environment : temperature, humidity, smoke detection
 - display information/Internet info : HDMI/Peritel TV output / simple remote controller
 - communicate with remote units via low power, 10s of metres
 - person detection

Remote units
 - temperature/humidity/smoke detection
 - person detection
 - control lights, heating