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Two 2A solid-state relays, two 20A electromechanical relays; Fused outlets.

Two SHT11 digital humidity/temperature sensors

One internal thermistor, three extra external thermistors.

Arduino BT board, using a bluegiga bluetooth 2 modem.

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The SHT11's do 12/14-bit readings, which make for more precise readings than with the thermistors.

Bluetooth is not really 100% necessary, but makes for easy wireless integration, while also transparently implementing pairing/passwords, encryption, and data reliability.

There are a few low-baud (2400bps) modems that are cheap - ones from radiometrix used for telemetry purposes. The problem with these is the need to code for reliability and security. Whenever you add wireless, along comes susceptibility to outside interference, etc. Not to mention the cost, if a computer is available nearby then it would not be necessary.

To give you an idea of the difference between the avr's 10-bit adc hooked up to a thermistor in a voltage divider:



This is about 0.2 degrees F steps, in the above pic manifested as jagged lines. The SHT11's readings are much more resolute:



Btw, that bit of software isn't complete yet, but the pictures should give you an idea. You get what you pay for, too... A parallax 28018 (a DIP breakout board with the SMT SHT11 and optional pullup resistors, is $30 from mouser.

Hope that helps.