The three home automation standards supported by Thinking Home 2 are X-10, INSTEON and 1-Wire. Each has its own strengths.
The X-10 standard was created by the company of the same name. It is the oldest and has the widest variety of hardware to choose from. In addition to North American models, there is wide selection for Europe and Australia. X-10 is generally the least expensive.
INSTEON, from SmartLabs, is newer and much more reliable. In fact, the more devices that are installed, the better they communicate. This is because each device relays messages and this helps ensure each message reaches its destination. The selection of products is very good and growing fast.
1-Wire, from Maxim, uses a dedicated cable instead of using the home wiring. This is the most reliable approach. The hardware is not generally designed for lamps and appliances, though. Thinking Home supports temperature sensors via 1-Wire.