If you need only one or a few of the devices, than a simple approach, especially if you're not that familiar with microprocessors, may be to use Stamp components from Parallax, Inc. They sell microprocessor modules that are easy to program (in BASIC) and RF modules that can communicate between uP's. You'd program one uP to transmit the message and a second to receive and display it.
I've used one of their uP modules with good results. You simply plug the module into your computer's serial port and it's ready to program.