I can't see the e-bay link - is that for parts like these?http://www.robotshop.com/search/search.aspx?locale=en_us&keywords=434
They work well with virtual wire to ensure that the receiver only passes on valid data:
RF ASK Transmitter/Reciever Example
// This code depends on the VirtualWire Library for Arduino and is
// based on the example code provided by Mike McCauley (firstname.lastname@example.org
// See VirtualWire.h for detailed API docs.
// This example shows how to use the VirtualWire library to send and receive
// simple messages and use them to control digital I/O pins. Buttons are
// connected to the transmitting Arduino on pins 8-11 (to ground, internal 20k
// pull-up resistors are set in the code) and in the same fashion,
// LEDs are connected to the recieving Arduino on pins 8-11. When a button is
// pressed on the transmitter, the corresponding LED will light on the reciever.