Well you would needthe following:
1. A cheap computer (anything old with a 400Mhz or above will work) I use an old desktop without a monitor and VNC into it. Make sure that the PC has 2 free serial ports.
2. Firecracker transmitter and as many appliance modules as you need ( 1 appliance module for each device you need to control)
3. A temperature monitor kit from http://ozitronics.com/data.html#k145
4. Software like Misterhouse (Free) http://w3.misterhouse.com:81/ or Homeseer. I use Homeseer http://www.homeseer.com/
5. An internet connection if you want to control and monitor the tank while away.
6 Optional webcam to be able to see your tank from anywhere.
I can give you more details on how to setup everything if you need it.
Asad