If you use a low-cost prebuilt relay board like one of these, you don't need a breadboard. http://goo.gl/8ZEQ8
And if you use a sensor shield and pre-made cables, you don't need a protoboard either. Take a look at:
Arduino Power stuff here: http://arduino-info.wikispaces.com/ArduinoPower
Arduino cabling here: http://arduino-info.wikispaces.com/Cables
And if you get one of these new Arduino-Compatible boards with 3-pin cable connectors built-in, all you need is a relay board (for up to 4 relays, more and you need a separate 5V supply).http://arduino-direct.com/sunshop/index.php?l=product_detail&p=225
IF your application only turns on 1 or 2 relays at a time in controlling the big device, you don't need an added power supply.
DISCLAIMER: Mentioned stuff from my own shop...